To mess with the MVS and AES subject again,the Phantom 1 worked well, I had one a couple of years back before I switched over to MVS stuff. The problem with it was not liking newer games,and the death grip it had on carts. It was hard to place on and remove carts. For the price you would have to spend on a AES console and a Phantom 1 or Super MVS converter you could afford to buy a consolized 2 Slot and some games.
MVS carts are far cheaper,and are constructed better then the AES carts. You also have a larger selection to choose from readily available on ebay and other net shops dealing in arcade hardware. Average MVS cart prices tend to be from $7-90 depending on the game. If you want to own Shock Troopers or Blazing Star its a easier task with a MVS in your hands.
Yea the NEO has a ton of fighters,but it also has a ton of other types of games,shooters,top view racers,puzzle titles,action games,and sports games. The Saturn is a great system too,for its 2d and its 3d depending on the games you plan to buy. Neither system can do wrong in my eyes.