I don't like pistol grips on shotguns and I don't trust safeties. But if you do, you probably want an 870 - the 870's safety is on the trigger guard, and the 590's is on the tang, where it's impossible to manipulate with the firing/trigger hand.
I have had a 590 for 10+ years now and like it. I looked at 590A1's at a gun shop the other day and was impressed with the width of the barrel walls. I don't imagine I'll ever bayonet anyone (to begin with, I don't own a bayonet) but Murphy has a way of making things break/bend/dent at the worst possible times, and the 590A1 looked more durable/idiot-proof. If I had it to do over, I'd buy the 590A1 over the 590. The 590 is nothing to sneeze at, however.