Well, I find males to be more cuddly and friendly while females are naturally aloof. However it depends upon the individual Guinea pig though. Females do smell less. Both suffer from an equal number of health problems at old age. Males require constant cleaning of the anal sac when they are impacted (happens a lot in older boars). While I've heard that older sows should be spayed in order to prevent ovarian cysts. Not all males fight. Brothers brought up together since birth may get along very well. I've also noticed several sows that fight and have had to be separated because they get too vicious. Males tend to be louder than females and tend to pee and poop wherever they run(again depends on the individual pig). However I've also noticed sows spray urine on the cage walls (and unfortunately outside the cage too) so I wouldn't call them particularly cleaner than males. Poop is poop, so as far as I've noticed males and females poop the same. Apart from the size of the poop there's nothing much that's different. All male guinea pigs I've known have been very friendly and outgoing while some females have been the same too. In short, look for a Pig that's seems interested in playing and has bright eyes and isn't looking very lazy.
