Q (Takenoko): If Saber Alter and Berserker seriously fought each other, which of them would
be stronger?
N: Dark Saber has lost what you call the protagonist’s compensation, or the glimmer of the
stars. So a miracle wouldn’t happen even against Gilgamesh, it would be just a measure of their
skills…
T: If it’s not in life but as Servants, wouldn’t it change a lot depending on who the Master is?
N: Back when they were alive, both had extraordinary magical energy output so it would be a
measure of their firepower. WIth Gilgamesh’s omnipotence and cunning (INT), Gil is slightly
advantageous here. If it’s a Servant battle, Dark Saber can win against Gil if the “Master’s
capacity as a Mage” is high. Gil can win against Dark Saber if the “Master’s charm as a human”
is high.
T: What does that mean?
N: It’s because Gilgamesh tries to fight only with his own power, regardless of his Master being
a first-rate or third-rate Mage.

Heaven's Feel II Booklet Nasu & Takeuchi Q&A