I don't know the answer to that. I wonder if one of Kinsey's publications sheds any light on it. Or you could try running a poll.
It is interesting to speculate, though. So how often we j/o depends on how often we get horny enough that we want to cum and how much opportunity we get to cum in other ways such as oral or penatrative sex.
Dealing with the first bit, getting horny seems to have two components. Partly it just seems to be at a minimum just after we've cum and then gradually build up so the longer it's been since our last orgasm the more we want to. That's the kind of horniness that you'd still have even if you lived on a desert island with no-one else there, and no porn, to stimulate you. This is almost certainly a function of testosterone. Then, on top of that there's whether anything external has provided some extra stimulation, e.g. seen someone attractive etc.
So looking at testosterone, part of the argument about "born this way" is that there are physical differences between gay and straight brains. We do know that there are other ways in which male and female brains differ and it is believed ante-natal testosterone is responsible. If finding women attractive is part of the way the brain is masculinised in the womb then that would suggest that straight men have a higher level of ante-natal testosterone than gay men. If that was true, and furthermore predicted higher testosterone from puberty onwards, then you might expect straight men to be hornier. There are ifs here, though. I don't know if anyone knows for sure whether ante-natal testosterone is part of the mechanism for setting who we are attracted to or whether there is a link between ante-natal testosterone and testosterone from puberty onwards.
But then consider that there are penty of hairy, bald gay men. Now I think there is more to this than just testosterone or black men, who on average have higher testosterone than white men, would tend to be hairy and bald and there are not especially. So I think there may be differences in how sensitive our hair folicles are to dihydrotestosterone and maybe differences in how much testosterone gets converted to dihydrotestosterone too but it means there are plenty of gay men who don't have oobviously low testosterone.
So what about external stimulation? I know that can make a difference because I have been in situations where I have been extra horny, for example the time my wife (then my g/f) and I had sex five times in one day at a music festival. In a primarily male work environment gay men would receive more external stimulation than straight men and may go home from work hornier. In a mainly female environment the reverse would be true and in a much more mixed environment there may be no difference.
Then on the question of other sexual outlets do straight men find getting partners easier as they can flirt more openly and in more situations? Or does men's tendency to be satisfied with meeting just for sex without any emotional/romantic connection work in favour of gay men?
So I think it comes back to "we don't know".