So...I was bored and actually searched for some studies on gay men and body image from my university's online portal. There's quite a surprising amount of articles dedicated to the question of gay men's body image fixation (dozens!), most of which seemed to be based on statistical analysis of surveys.
Quickly browsing through the abstracts, one comes to the conclusion that gay men on average are prone to problems with their body image. This is then correlated with low self-esteem and depression (that is to say: the more depressed you are and the lower your self-esteem, the more you're concerned with your body image). Moreover, fixation on the body seems also to be correlated with internalized homophobia/heterosexism. There's some inconsistency in whether your fixation on your own body reflects into your view of other people, but research literature mostly seems to suggest that the more concerned you are about your own looks, the more you are concerned about others' also.
In the light of all this, if gay men really are more superficial in the sense of being concerned about looks, one should always remember that fixation on the body image is a symptom of self-esteem issues and depression (and, as statistics can tell us, gay men are more prone to such things).
As for the claim that gay men are just as concerned about looks as straight men or women of any orientation - well, this is not true, at least according to some research I found. For example,
this study concludes, when comparing gay/bi men and gay/bi women, that
"males are considerably more preoccupied with and affected by physical appearance. Males reported significantly higher levels of image fixation, antifat attitudes, dislike of fat people, weight locus of control (indicating internal loci), physical discrimination, weight discrimination, and depression."
Most of this stuff is not freely accessible (so much for the transparency of science!) but
here is one good free example of this type of research.
It's all quite interesting, really.