It depends on the game, what looks better, what is animated better and what is more fitting for the story.
In Fire Emblem games I'll always play as a male because of the relationship system. In Bloodborne I played as a female and tried to model it from another character. The males were ugly in that game and the story doesn't relate to me as an individual. I'm not an extension of that character but rather playing that character. For Mass Effect I felt that Femshep is better than male Shepard, though in Andromeda I really wished I went with Scott over Sarah because he was a much better written and relatable character.
MMO's are dependent on race and appearance. In WoW I was Dreanei male who was fucking bad ass. Games like Black Desert online or other more realistic MMO's with intensive character creators I often go with a female but use my username and it's quite clear I'm a male. Often those games over sexualize the characters of both gender and it's not uncomment for girls to play male characters for the same reason. So I definitely factor in a lot of things. I have no problem with playing either gender and I embrace diversity in gaming. So I guess it all comes down to the game and the style and what I think I'll get out of that particular experience.
