I definitely like the Fate/zero Saber more than I like the Fate/stay night Saber. Specifically, Fate/zero Saber > Unlimited Blade Works movie Saber > Carnival Phantasm Saber > Fate/stay night game Saber > Fate/stay night series Saber.
I probably like the Fate/zero Saber best because she seems sensible and not retarded. That has always been my biggest beef about the Fate/stay night Sabers. She seems a little...slow in both the game and the television series. I guess she also seems kinda slow in the Unlimited Blade Works movie, but it's less objectionable there because of her diminished role. In her game route and the anime series, she and Emiya are infuriating. Most of the fault lies with Emiya. Famously, the player quickly realizes that the correct choice in the game is always the "noblest" one in accordance with the Otaku Virtues and never the intelligent choice.
Carnival Phantasm is amazing, but Saber hasn't been in it enough to surpass the Unlimited Blade Works version. Carnival Phantasm does have an enormous ensemble cast, after all.