Oh, look. Another gay thread. *rolls eyes* 2015 already ended, didn't it?
They can be as good as or better than heterosexual parents, sure, but that doesn't mean the upbringing will be as healthy. A child needs a mother and a father (not figures, actual mom and dad) throughout their life, and mostly through their adolescence, to gain different qualities and virtues from members of both sexes. However you try to twist it, having two "fathers" or "mothers" will undoubtedly influence the child in one way or another. Also, why the hell is everyone talking like gay parents are angels personified, while hetero ones are worthless scum? Lmao, most of you probably haven't even seen a gay couple.
With that being said, my personal take is that it depends on the gay couple doing the adoption. However, a hetero couple that's equally good at parenting as a gay couple will always be the better choice.