I would lean slightly towards St pro. It is a deeper game already and the code update will tip it. KM multiball isn't easy to get to as you are supposed to build the jackpots for it in the modes so timing out each mode is a waste of time and not the way its meant to be played. there are 18 missions and the way you do them can affect your gameplay etc.
Also bang for buck the ST pro pretty much is the same game as the premium with awesome flow.
All that said Im getting an IMV in about 3 weeks so I will probably change my opinion when that hits the garage floor.