After playing both it was a no brainer. We're not talking about a game like MET where there really is no difference - magna slings alone imo are worth it. There is a brand new ramp, ecto Google's, etc. So much more is loaded into it that it's prob the clearest prem vs pro I've seen.
If you know the theme is for you, it's even a more clear choice.
On a side note I recently bought MET and it's no question the surprise hit of the year. Wow is that game fun. It's actually so good even though the prem doesn't add much I was thinking about upgrading just so I have it all! Not sure I like the position of the hammer but love the smash feature.