Male or Female Dog?
Female for many of the reasons already stated:
They are more protective.
No chance of a "Junk Encounter" when giving belly rubs.
They don't pee on everything to mark their territory.
They seem a little smarter for some reason and are easier to train.
They don't seem to have the need to escape every evening and meet all thier dog buddies.
The Downsides are:
They certainly seem quite a bit bitchier.
Spotting if not fixed, plus all the male dogs that will come "Rooting Around for Romona".
Usually a bit smaller than the males if that's an issue.
So, that's my opinon. :)