Funny. I've always heard opposite! Girls average potty training a few months earlier than boys (according to Baby Center).
I think the key is to wait until they are ready and then it doesn't matter the gender, they are both pretty easy (compared to trying to train when they are not ready).
Barebummed gets the best results in my opinion. No pull ups, no diapers, no underwear, no nothing...just bare bums. They think about it differently when they have nothing on them. They are much more aware.
And, yes, siblings are very helpful in potty training, in my opinion. :-)