I currently have 2 up and running Mame cabinets, with a several more in the works.
I DO NOT put the same games on them. The 112 games on my Artic Mini are not on my Amazing Maze. Battlezone and Bradley Trainer will come off the Amazing Maze as soon as I get my Battlezone Mame cabinet up. Once I put together my Space Firebird Mini, then all the vertical 8-way games are coming off my Amazing Maze as well.
Likewise, any other specialty cabinets I make (vertical spinner or vertical trackball is probably next) will have their games immediately removed from the game list on the Amazing Maze.
If you are just going for two cabinets, then the best second cabinet is vertical 4-way, either cocktail or upright (doesn't matter, almost all vertical 4-way games support cocktail mode).
If you are going the mega-multi cabinet route like I am, then the LAST one to do would probably be either horizontal spinner, or horizontal 4-way. Not a lot of games go that route.
Unfortunately to play EVERYTHING correctly with the correct orientation with no rotating monitors or machiness with excess controls, you need like 20 cabinets. And that isn't even counting those few games that mix controls (Tron, Snake Pit, etc). I may never support those titles.
When complete my Mame-Cade will have the following.
Horizontal with Streetfighter controls (already done).
Vertical with 4-way and 2 buttons (already done).
Battlezone cabinet (have cabinet, and all components needed except for the monitor overlay).
Vertical 8-way - (have cabinet and all components needed).
Other cabinets/panels I am considering (basically because I already have the controls).
Spinner, trackball, dual analog sticks (without buttons on them), single analog stick with buttons on it, positional gun, and top fire 8-way (have several styles of these). Probably won't ever do a driving cabinet or panel, I would rather just spend the cash to get a Roadblasters or Turbo cockpit, or an Outrun upright.