I'd much rather have a girl. Emotionally it may be more difficult, but energy wise I think girls are easier. i.e. a 5 year old girl can understand that mommy is sick and will usually agree to snuggle in the bed with her and watch Kim Possible for a few hours, then bring some toys into the bedroom and play for a while, then try on a bunch of clothes... and she'll usually agree to help clean up with you, too.
A 5 year old boy, on the other hand, would be pretty unusual if he sat quietly in the bed watching TV for several hours. =P At best, most of the boys I know would have several car crashes with their toys (sound effects included) then wander out of bed after a few minutes and get into trouble >_<
But I don't have a lot of experience with kids. Just 3 younger brothers, 2 younger sisters, current and previous work in childcare and babysitting, and several years worth of nannying. :P