Lol, it would depend on if you actually love the guy.
If you love the guy, then it's worst if it was a male. && the reason why I say that is because you can't compete with a male, you have no penis; you're not a dude.
Now if you're with someone just for the sake of being with them, (or the relationship hasen't evolved into love yet) then cheating with a female is worse. Like queen bs said,
if he cheats with a guy "oh well, he's just gay" and if he cheats with a female there's no actual way of justifiying that shit.
- In the end, cheating is cheating so there both horrible.