There is not even nearly enough information to know the answer.
What would be the quality of some other, say heterosexual, foster home?
What is the quality of life in this foster home?
and so on with so many questions which have no anwers.
However, if you are trying to prove that gay parents are equal to heterosexual (foster) parents - they are not. That's why they are called gay and not heterosexual.
That doesn't mean that gay parents would have nothing to offer, but only means that they by definition lack something essential - exposing their children to influence of two parents of both sexes.