Well I think it entirely depends on the child, but speaking from experience my DS was easy to potty train, much much easier than my Isabelle right now.
This is how I see it: girls are easier when they are little and boys are easier when they are older.
Boys aren't picky about their clothes, they don't have fights with their BFF, plus you just don't worry as much about them as you do with girls. My DH already has nightmares when DD#1 starts dating.
But DS gets into more trouble at school. (I couldn't even tell you how many phone calls I've gotten) It takes more effort to get him to do his work. And I find that he's not as mature as DD was at his age.