Early game on ahri with 9 in defence and 9 armour in seals and a dorans ring, and talon with long sword and typical masteries. Only runes change.
Combo = E AA Q (IF BOUGHT TIAMAT) W (R IF LEVELED) AA (CRIT IF YOUM/IE)
**LEVEL = 3 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 21.438749999999995
Real HP of Ahri = 749.84
EHP OF Ahri = 910.596323
AA Damage = 82.18848235294118
Q Damage = 151.30848235294118
W Damage = 86.88
R Damage = 0
Combo Damage = 444.1433321411766
% of her EHP gone = 48.77499732020954
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 32.958749999999995
Real HP of Ahri = 749.84
EHP OF Ahri = 996.977891
AA Damage = 90.73848235294118
Q Damage = 170.97348235294118
W Damage = 97.14
R Damage = 0
Combo Damage = 495.80243214117644
% of her EHP gone = 49.730534309428975
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 13.758749999999996
Real HP of Ahri = 749.84
EHP OF Ahri = 853.008611
AA Damage = 75.43848235294118
Q Damage = 135.78348235294118
W Damage = 78.78
R Damage = 0
Combo Damage = 403.35983214117647
% of her EHP gone = 47.28672453473936
_______________________

**LEVEL = 4 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 24.037850000000002
Real HP of Ahri = 814.936
EHP OF Ahri = 1010.8290932760001
AA Damage = 85.19175764705882
Q Damage = 155.02675764705884
W Damage = 137.54
R Damage = 0
Combo Damage = 508.7879419388235
% of her EHP gone = 50.33372558459814
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 35.55785
Real HP of Ahri = 814.936
EHP OF Ahri = 1104.709720476
AA Damage = 93.74175764705882
Q Damage = 174.6917576470588
W Damage = 147.8
R Damage = 0
Combo Damage = 560.4470419388235
% of her EHP gone = 50.7325165652871
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 16.357850000000003
Real HP of Ahri = 814.936
EHP OF Ahri = 948.242008476
AA Damage = 78.44175764705882
Q Damage = 139.5017576470588
W Damage = 129.44
R Damage = 0
Combo Damage = 468.0044419388236
% of her EHP gone = 49.35495767488652
_______________________

**LEVEL = 5 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 26.752100000000002
Real HP of Ahri = 882.916
EHP OF Ahri = 1119.114571236
AA Damage = 88.30372235294118
Q Damage = 158.8537223529412
W Damage = 188.2
R Damage = 0
Combo Damage = 573.8012262211765
% of her EHP gone = 51.272786626971076
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 38.2721
Real HP of Ahri = 882.916
EHP OF Ahri = 1220.826494436
AA Damage = 96.85372235294118
Q Damage = 178.51872235294115
W Damage = 198.45999999999998
R Damage = 0
Combo Damage = 625.4603262211765
% of her EHP gone = 51.232532147013075
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 19.072100000000002
Real HP of Ahri = 882.916
EHP OF Ahri = 1051.306622436
AA Damage = 81.55372235294118
Q Damage = 143.32872235294118
W Damage = 180.1
R Damage = 0
Combo Damage = 533.0177262211765
% of her EHP gone = 50.70050115218644
_______________________

**LEVEL = 6 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 29.581500000000002
Real HP of Ahri = 953.78
EHP OF Ahri = 1235.9224307
AA Damage = 91.52437647058824
Q Damage = 162.78937647058825
W Damage = 188.86
R Damage = 276.075
Combo Damage = 878.8226849882353
% of her EHP gone = 71.10662151268579
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 41.1015
Real HP of Ahri = 953.78
EHP OF Ahri = 1345.7978867
AA Damage = 100.07437647058825
Q Damage = 182.45437647058824
W Damage = 199.12
R Damage = 288.9
Combo Damage = 944.0762849882353
% of her EHP gone = 70.14993070788535
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 21.901500000000002
Real HP of Ahri = 953.78
EHP OF Ahri = 1162.6721267
AA Damage = 84.77437647058824
Q Damage = 147.26437647058825
W Damage = 180.76
R Damage = 265.95
Combo Damage = 827.3066849882354
% of her EHP gone = 71.15563072251256
_______________________

As you can see, in the early game the difference is negligible.

Early-Mid Game on ahri with a fully stacked seekers and 2 dorans, and talon with tiamat and brutalizer.

**LEVEL = 9 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 75.7606
Real HP of Ahri = 1245.476
EHP OF Ahri = 2189.056090456
AA Damage = 156.83847529411764
Q Damage = 341.74847529411767
W Damage = 356.84000000000003
R Damage = 361.05
Combo Damage = 1655.2128920094117
% of her EHP gone = 75.61308726742656
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 87.28059999999999
Real HP of Ahri = 1245.476
EHP OF Ahri = 2332.5349256560003
AA Damage = 165.38847529411765
Q Damage = 361.4134752941177
W Damage = 367.1
R Damage = 373.875
Combo Damage = 1729.5294920094123
% of her EHP gone = 74.14806410767893
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 68.08059999999999
Real HP of Ahri = 1245.476
EHP OF Ahri = 2093.403533656
AA Damage = 150.08847529411764
Q Damage = 326.22347529411763
W Damage = 348.74
R Damage = 350.925
Combo Damage = 1596.5418920094119
% of her EHP gone = 76.26536720424609
_______________________
**LEVEL = 10 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 79.0506
Real HP of Ahri = 1327.876
EHP OF Ahri = 2377.569945256
AA Damage = 160.49388705882353
Q Damage = 386.11888705882353
W Damage = 357.5
R Damage = 361.875
Combo Damage = 1716.2187851858826
% of her EHP gone = 72.18373485121978
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 90.5706
Real HP of Ahri = 1327.876
EHP OF Ahri = 2530.5412604559997
AA Damage = 169.04388705882354
Q Damage = 405.78388705882355
W Damage = 367.76
R Damage = 374.7
Combo Damage = 1790.5353851858824
% of her EHP gone = 70.7570120735052
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 71.3706
Real HP of Ahri = 1327.876
EHP OF Ahri = 2275.589068456
AA Damage = 153.74388705882353
Q Damage = 370.59388705882355
W Damage = 349.4
R Damage = 351.75
Combo Damage = 1657.5477851858827
% of her EHP gone = 72.8403826579523
_______________________
**LEVEL = 11 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 82.45575
Real HP of Ahri = 1413.16
EHP OF Ahri = 2578.3916767
AA Damage = 164.25798823529414
Q Damage = 390.5979882352941
W Damage = 358.15999999999997
R Damage = 462.7
Combo Damage = 1841.3085636235298
% of her EHP gone = 71.41306653534349
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 93.97574999999999
Real HP of Ahri = 1413.16
EHP OF Ahri = 2741.1877087000003
AA Damage = 172.80798823529412
Q Damage = 410.2629882352941
W Damage = 368.41999999999996
R Damage = 475.525
Combo Damage = 1915.6251636235295
% of her EHP gone = 69.88303491744492
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 74.77574999999999
Real HP of Ahri = 1413.16
EHP OF Ahri = 2469.8609887000002
AA Damage = 157.50798823529414
Q Damage = 375.07298823529413
W Damage = 350.06
R Damage = 452.575
Combo Damage = 1782.6375636235296
% of her EHP gone = 72.17562331561876
_______________________

Not much of a difference yet either.

Mid-Late game vs ahri with zhonays, 2 dorans and talon with tiamat, LW, bruta
**LEVEL = 12 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 45.95092500000001
Real HP of Ahri = 1377.7279999999998
EHP OF Ahri = 2010.8067599839999
AA Damage = 208.1307788235294
Q Damage = 527.1857788235294
W Damage = 406.82
R Damage = 523.525
Combo Damage = 2250.9622273223526
% of her EHP gone = 111.94323950553378
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 57.47092500000001
Real HP of Ahri = 1377.7279999999998
EHP OF Ahri = 2169.5210255839997
AA Damage = 216.6807788235294
Q Damage = 546.8507788235295
W Damage = 417.08000000000004
R Damage = 536.35
Combo Damage = 2325.278827322353
% of her EHP gone = 107.1793635508292
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 38.270925000000005
Real HP of Ahri = 1377.7279999999998
EHP OF Ahri = 1904.9972495839997
AA Damage = 201.3807788235294
Q Damage = 511.66077882352937
W Damage = 398.72
R Damage = 513.4
Combo Damage = 2192.291227322353
% of her EHP gone = 115.08107047404349
_______________________

Mid-Late game vs ahri with zhonays, 2 dorans and talon with tiamat, LW, Youm

**LEVEL = 14 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 40.58685000000001
Real HP of Ahri = 1562.7160000000001
EHP OF Ahri = 2196.9731988460003
AA Damage = 221.20242823529412
Q Damage = 588.1874282352942
W Damage = 414.14
R Damage = 532.675
Combo Damage = 2784.5136140047066
% of her EHP gone = 126.74317626939293
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 52.10685000000001
Real HP of Ahri = 1562.7160000000001
EHP OF Ahri = 2376.9980820460005
AA Damage = 229.75242823529413
Q Damage = 607.8524282352942
W Damage = 424.4
R Damage = 545.5
Combo Damage = 2873.5704140047064
% of her EHP gone = 120.89073338802534
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 32.906850000000006
Real HP of Ahri = 1562.7160000000001
EHP OF Ahri = 2076.956610046
AA Damage = 214.45242823529412
Q Damage = 572.6624282352941
W Damage = 406.03999999999996
R Damage = 522.55
Combo Damage = 2714.2056140047057
% of her EHP gone = 130.6818640734431
_______________________

Here comes the HUGE difference.

LATE GAME vs ahri with zhonays and talon with hydra, IE, youm and LW.
**LEVEL = 16 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 45.51187500000002
Real HP of Ahri = 1759.24
EHP OF Ahri = 2559.90310975
AA Damage = 334.70883529411765
Q Damage = 839.6238352941177
W Damage = 541.46
R Damage = 791.825
Combo Damage = 4479.571090035295
% of her EHP gone = 174.9898686779895
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 57.031875000000014
Real HP of Ahri = 1759.24
EHP OF Ahri = 2762.5675577500006
AA Damage = 343.2588352941176
Q Damage = 859.2888352941176
W Damage = 551.72
R Damage = 804.65
Combo Damage = 4578.947740035294
% of her EHP gone = 165.74971088723933
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 37.83187500000001
Real HP of Ahri = 1759.24
EHP OF Ahri = 2424.7934777500004
AA Damage = 327.95883529411765
Q Damage = 824.0988352941176
W Damage = 533.36
R Damage = 781.7
Combo Damage = 4401.115840035295
% of her EHP gone = 181.50477062975077
_______________________
**LEVEL = 17 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 48.08280000000002
Real HP of Ahri = 1861.8280000000002
EHP OF Ahri = 2757.0470335840005
AA Damage = 339.1250729411765
Q Damage = 844.7550729411764
W Damage = 542.12
R Damage = 792.65
Combo Damage = 4742.109279115296
% of her EHP gone = 171.9995785835699
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 59.602800000000016
Real HP of Ahri = 1861.8280000000002
EHP OF Ahri = 2971.5296191840007
AA Damage = 347.6750729411765
Q Damage = 864.4200729411765
W Damage = 552.38
R Damage = 805.475
Combo Damage = 4846.538979115296
% of her EHP gone = 163.09913075832586
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 40.40280000000001
Real HP of Ahri = 1861.8280000000002
EHP OF Ahri = 2614.0586431840006
AA Damage = 332.3750729411765
Q Damage = 829.2300729411766
W Damage = 534.02
R Damage = 782.525
Combo Damage = 4659.6647791152955
% of her EHP gone = 178.25402621571206
_______________________
**LEVEL = 18 **
_______________________

9 Armorpen Marks, 3 AD Quints
Real Armor of Ahri = 50.72600000000001
Real HP of Ahri = 1967.3
EHP OF Ahri = 2965.2325980000005
AA Damage = 343.65
Q Damage = 849.995
W Damage = 542.78
R Damage = 793.475
Combo Damage = 5008.838249999999
% of her EHP gone = 168.91889875277832
_______________________

9 AD Marks, 3 AD Quints
Real Armor of Ahri = 62.24600000000001
Real HP of Ahri = 1967.3
EHP OF Ahri = 3191.8655580000004
AA Damage = 352.2
Q Damage = 869.6600000000001
W Damage = 553.04
R Damage = 806.3
Combo Damage = 5118.320999999999
% of her EHP gone = 160.35515616162422
_______________________

9 Armorpen Marks, 3 Armorpen Quints
Real Armor of Ahri = 43.04600000000001
Real HP of Ahri = 1967.3
EHP OF Ahri = 2814.143958
AA Damage = 336.9
Q Damage = 834.47
W Damage = 534.6800000000001
R Damage = 783.35
Combo Damage = 4922.4045
% of her EHP gone = 174.91658470444173
_______________________

HUGE DIFFERENCE LATE GAME!!!