The pro is an amazing game. Easily one of the best I've ever played. My initial plan was to keep the Pro until I can upgrade to the Premium, but now I'm just going to keep the Pro because all of the fun is there.
The extra mechs are really cool, and you can't argue they don't make the game more immersive and interesting. However, my opinion, they don't add enough to the actual gameplay to warrant an upgrade. And I like having the Mechagodzilla spinner available at all times.
All that being said, I would have gotten the Premium if I had the chance initially. I got lucky and found a Pro while waiting on a Deadpool that's been pushed back to late this year. I'm glad I did, otherwise I would not have given the Pro a chance and now I have all that extra cash to spend on another pin