As a girl who's done both, this is what I've learned:
1. It's a lot easier for two girls to have sex in a shower...
...than it is for a straight couple to have sex in a shower.
2. Men somehow grow hair everywhere.
But girls are so smooth.
3. Your partner assumes you desperately want to have sex with a penis, no matter who you're with.
So men think that they're giving you a great gift just because of what's in their pants.
And women are constantly concerned that you'll leave them for a man.
4. Being the same gender often makes for perfect cuddling size.
(Sorry. If this isn't true for you, I feel for you.)