If you are planning to build your collection quickly beyond 3 pins, I see no good reason to go beyond a pro for starters. It's not like the pinball collection judges show up and ding you for style points for getting a pro. Now, if you are only going to add another pin every 2-3 yrs, then it makes sense to step up to the premium level (If the game warrants it...)

OK, now that I have said that, I would recommend going for 1 of either TWD prem - OR - MET pro or Prem AND Then 1 of either AFM or MM.

SO, a 2 game collection, huh.... Any of the suggestions would work. You know, for long term play-ability it is hard to beat AFM or MM. Then throw in TWD, Met, SW or any of the recent Sterns and you can't go wrong. People love TWD for the rule set, but I am not in love with the theme, as I am not into Zombie culture. The other thing you can do is just get whatever 2 are easily accessible and plan to swap out wholesale every 2 yrs... TWD & SW would be awesome.