Gray (Fate) looks a lot like Saber and has similar abilities but those won’t be enough to win here. It is rare that the fake can beat the original after all. Saber still has better speed and power at her disposal which will really make things difficult for Gray. It would be extremely hard for her to keep up with Saber after all and a single strike could be decisive in this match. Gray won’t be able to counter in time. Saber wins.