I'm attracted to feminine and genderqueer males. I definitely prefer cis males, from a purely physical perspective, in the same way that I prefer red or black hair, dark eyes, and Asian features. They aren't essential, but they are very nice as frosting on the cake. The cake is more important, though. I can't be in a relationship with someone if I can't be really good friends with them. If I fell in love with a trans guy, so be it. I'm not real turned on by trans-male anatomy, probably because I have Issues related to my own body, but I'd figure out a way to make it work.
I would not date an MtF, though. That's not because I'm a cissexist jerk. It's because I'm gay, and I'm particularly attracted to feminine men. I'd be attracted to her male features, and that would be completely unfair to her.