A pusher behind the CofG can make a machine want to swap ends (depending on tail) and want to push over if anywhere near negative, where as a tractor will always try to pull itself straight, so in that sense, the tractor is more stable..... however, tractors have their own issues including all of what Birdy said and also that the pilot has less forward view and sits in the prop blast so screen is quite handy.... the pilot tends to block the tail, so although a bare bones frame can work, a more streamlined rear fuselage is more desirable. Tail dragger tractor gyros can have issues with prop strikes if fitted with to effective brakes (Jam on the brakes and it stands on its nose)... that's why some have a nose wheel or skid even tho they are tail draggers. Plenty of them around, which is great to see, but I doubt if they will ever come close to scratching the market for pushers. I have seen 4 myself, and videos of others, but the only one I have seen fly is our little wing over here.... one time.
either they are less fun to fly, or more difficult to fly.... I don't know? I think you would find if tractor was a better 'all round' machine, then all of the musterers would be using them. Birdy, how many musterers use tractors to muster all day every day?
I doubt many at all? 
