I’m pretty new to the competitive scene, so I’d love to hear people’s feedback on my thinking.
I can only fit one game in my small NYC apartment, so I chose Spiderman. Here was my thinking.
- 3rd flipper allows me to practice staging.
- Shot behind third flipper which is tighter than the one on ST would make me better at that shot.
- You can backhand most shots.
- Practice live catching out of the pops.
- Practice loop passes when post is down. (Or disable the post.)
- To start modes you are required to hit every shot, so lots of practice on different shot types.
- Shot doublers and stacking multiballs require strategy.
It also doesn’t hurt that it is one of my top 3 games. 
After owning the game for almost two years I think I’m ready to put another machine in it’s place. But for the purpose of practicing I think it was a great machine. Having said that, it does violate what @cayle said, scores are pretty linear and require long ball times.