I would buy new. I don't mind used if I know where it came from and how it had been taken care of. If you find a used one check for excessive wear in the finish, corrosion and stuck choke tube.
Any of the above mentioned guns would be good as long they fit you properly. My personal favorite is my M2. Shoot clays, pheasants and waterfowl with mine.
I replaced the one on my son's supernova with a m2 front sight bead. Can get them from brownells. Made all the difference in the world installing the smaller sight.