Quoted from Cobray:

You want to hear something funny? I had an Iron Maiden Pro and loved it so much that I sold it and bought a (HUO/Used) Iron Maiden Premium. Guess what? I didn't like the Premium nearly as much as my Pro!! The extra features didn't help the flow and gameplay for me and it just never felt as good to play as my Pro. To this day, I regret getting rid of my pro for the premium! Everyone kept telling me I'd like the Premium better!! Nope.
This is NOT to say that GZ Pro is better than GZ premium.. just that sometimes extra features don't equal better gameplay... to some. Now there are games that I absolutely prefer the premium version of, but I have determined that the only true way for ME to know is for ME to play both. I know it sounds cliche, but it's what I try to go on IF I'M NOT SURE on a specific title.
That being said, on GZ, I have a Premium on order and am not looking back!! I played a pro on location and feel the Premium version is the one to own in my home.
Best of luck! Honestly you can't go wrong with either a Pro or Premium on GZ... it's a monster hit either way!!

Quoted from jeffspinballpalace:

GZ pro will make you happy. It is everything you’ll need and worth $7k price tag.
GZ premium will make you walk on clouds. It is everything you’ve wanted and worth the $12.5k price tag it will cost to get one this year. Is the premium worth $5.5k more? I said yes to one recently and am satisfied with the decision to get one now.
Best solution is buy GZ pro now and put a deposit with a distributor on a future GZ prem (with expected delivery 6/23) for $9.3k that is expected to cost $9.7k when it arrives. Congrats you have purchased 2 GZ pinball machines at msrp. The upgrades from pro have cost you $2.7k now and you sell one of your GZ’s.
I play a lot of GZ prem and ALSO GZ pro each week. The pro holds up really nicely and I’d be happy with one.