The argument needs all three routes

Fate/stay night is a long book about a boy who needs to be argued out of his ideals. It is also a book that spends a lot of its Fate route on Saber as a figure Shirou protects. The balance tips in the later routes — Rin's route lets her do the arguing, Sakura's route lets her stop waiting — but it takes playing all three to see the game's actual position on its women.

If I could recommend only one route, I would recommend none. The game doesn't work that way.