Everyone I talk to says male guppies shouldn't bicker, but mine do. When there was a third one in the tank, all three of them chased each other around. Luckily there hasn't been any fin nipping.
I still would choose two males over a male and female any day, unless you're willing to bring in a second female AND deal with all the fry.
It sounds cute to have baby fish, but even with fish (just like cats/dogs), I do think it's important that a person is responsible. If you don't have room for the babies, you shouldn't be getting male/females.