Gonna have to give my vote to C.A. on this one.
Out of the three, he is the one I am most familiar with. It's pretty amazing how much progress he has made since I first saw his works back on the Haruhi image thread a couple of years ago.
Of course, as a big fan of yuri, C.A.'s piece has an extra charm in my book!
HayashiTakara's piece is also very nice. Though, the nudity in it strikes me as a bit out of place.
yuuk1's work is nice and simple, although I still prefer the other two a bit more.