Personally I would opt for the male in your situation, although you never know. But in my experience Basenji males are less difficult and less likely to hold a grudge than the girls. A breeder I know comparing the sexes once said "the males are very sweet, but the bitches are such bitches!" My girls were definitely tougher than my boys, but that is anecdotal evidence. I do know that once a female has made up her mind that she dislikes another bitch she is unlikely to change. And just because that other female is bigger than her won't dissuade her if she takes a dislike. I did have two female Basenjis together, the older seven years when I got the younger as a pup, but I was lucky and they bonded like mother and daughter, so I never had an issue. You could be lucky and have a similar result, but if you're open to either sex I think the male is a safer choice.