I know that some gay men are effeminate and others aren't. What is the difference? Are the gay men who sleep with women, who are bisexual, more masculine than men who just sleep with other men?
Well, I would have to say definitely not, and not just judging by the number of "big queens" I've met who have or have had girlfriends or insist they're bisexual.
Most gay men are not stereotypical, and their outward demeanor -- be it butch or femme -- generally provides no clue to what they do in bed or whom they prefer to sleep with. There are "queeny" guys who are Tops, and very masculine men who are Bottoms. Macho guys who only sleep with guys, and not-so-macho men who [want to] sleep with other men but have wives or girlfriends.
In other words, it's a highly individual matter. In general, men who identify as bisexual -- rightly or wrongly -- do not have a more masculine demeanor than guys who identify as gay. Some, unfortunately, think they are more masculine because of the out-dated, pre-Stonewall thinking that says a man isn't a man unless he has sex with women. I don't need to comment on how tiresome and self-defeating that attitude is, but it does account for the "bisexual" label more often than many would like to admit.