Pokemon Version Differences

Q: Why are you playing this version? Why not the almost identical but slightly different brother version?

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Q: Why are you playing Blue? Why not Red?

A: So, let's go through every brother/sister game and compare the differences for speedrunning:

Blue vs Red:
In the ideal situation, both games are identical

Assuming you don't fight anything on route 1, Blue has a better back up strategybecause you will likely fight a Caterpie in Viridian Forest rather than a Weedle, and avoid additional chance to get poisoned

Time saved for Blue: Potentially the whole run, otherwise 3 seconds.

Assuming you don't get a Paras in Mt Moon, Blue has a better back up strategy in Sandshrew, a version exclusive pokemon, as it learns strength as well, and avoids having to get Lapras

Time saved for Blue: 13 seconds

However, assuming you run into Oddish/Bellsprout on Route 6? after catching Sandshrew, you lose time on that encounter, meaning Red would be faster.

Time saved for Red: 15 seconds

UNLESS!! You use Nidoking strats. If you do, you pretty much have to play Red, because the encounter rate of Nidoran Male is much higher on Red than on Blue.

Gold vs Silver:
In the ideal situation, Silver saves 2 frames of text (Silver Wing vs Rainbow Wing)

Assuming you don't find a Sentret or a Bellsprout, Gold has a backup strategy in Sandshrew, that learns both Cut and Strength

Time saved for Gold: 15-29 seconds, depending on your Totodiles Attack DV

Fire Red vs Leaf Green: any%:

These games are identical for speedrunning.

Fire Red vs Leaf Green Round 2:

Fire Red has 2 pokemon that you can buy for much cheaper than in Leaf Green at the casino, making 2 affordable in Fire Red but not Leaf Gren

Time saved for Fire Red: ~50 seconds if you run into Clefairy, ~2 minutes if not

Ruby vs Sapphire:

These games have different evil teams, and different legendaries. The hideouts are actually quicker in Ruby (camerupt and numels are easy kills for Mudkip) but Groudon ends up losing time on the Elite Four, so much so that Sapphire is faster

Time saved for Sapphire: 7 turns, ~49 seconds.

Heart Gold vs Soul Silver:

The only difference between these games is that you have to encounter the legendary birds. As such, in Heart Gold you must climb Tin Tower, and in Soul Silver you must complete Whirl Islands (in the dark)

Time saved for Heart Gold: ~75 seconds

Black 2 vs White 2:

The difference between these games come from the layout of different areas. The first plasma first adds an extra battle for White 2, but the second one has two less battles in White 2. Reversal Mountain also has one less battle.

Time saved for White 2: 2 battles, ~2 minutes

I haven't routed Diamonds vs Pearl, or Black vs White, will add when I do so.