Potter is great, and I've long championed him on here. But Arteta obviously should be kept on for next season. He had a good transfer window last summer, and despite not being able to attract the caliber of player the CL clubs could (or the clubs that can pay very big wages), they identified young players who could make an impact. Missing out on top 4 makes the summer a lot trickier though, they're going to have to do the same again, whereas CL football could have helped a lot.
This forum is fairly clueless when it comes to managers, Howe was getting slated when Newcastle went for him despite being an obviously good manager. When I mentioned Potter for United I was ridiculed.
There's more of a chance(Even if it's a very very slim one)happening under Potter than with Arteta. United have been shite for years now but there has always been the idea that the end goal will be winning the league, maybe I'm wrong here but with Arteta there doesn't even seem even the hope Arsenal could win a league title with him as manager.
Financially they're in different worlds though. People go on about transfer fees but wages are the big indicator, United have a wage bill well over double that of Arsenal. Even with United being shite they're still a juggernaut, and will always be an attractive club for players.