I don't date black men exclusively but there does seem to be an attraction between black guys and many middle aged white trannies. For me I think that there is an erotic attraction to the contrast of my very white complexion and my partner's brown skin. I also must admit I like the texture and sensation of a hot black guy's cock in my mouth and ass! Size isn't an end all for me but sometimes this t-gurl craves a big black cock!
I don't have any scientific evidence but it's been my experience that black men tend to cum more per ejaculation than their white counterparts. Probably the most important factor is that ALL of the black dudes that I have dated have accepted me for who I am and never had the nerve to ask dumb questions about my transition.
Here's me and a few male friends. The last one was taken with my camera phone just as my friend Eric was shooting his load