Obvious playfield differences are the VUK return to left flipper on Prem/LE vs. the saucer's sorta randomish kickout on the Pro, which I believe gets tied into the coil pulse strength(?) setting in the menu. Then there is the kickback in the left outlane on the Prem/LE that instantly puts the ball back into play vs. the ball save and auto launch to the pops on the Pro. Now, one might have an actual argument for which is better though. In my opinion(being a Pro owner), I like having it go to the pops because it gives me a free try at the warp ramp. But it does slow the game down considerably. On the flip side, you basically just got saved from draining a ball either way so no bitching allowed.
Another personal preference is the difference between the wireform and plastic ramps. Personally, and not in all cases, I actually prefer the plastic ramps on ST. I don't know if it's just the way it catches and reflects the light, how it looks along with the rest of the theme, and there's also a nice feel to them too. I'm very happy with them.
Yes, there are a few bells & whistle features of the Prem/LE that would be nice to have like the laser show for one. The lighted apron looks cool, although I could spring for the Refinery one if I wanted a nice powder coated interactive LED one. Illuminated side rails are a nice touch too.
I almost shudder to think how much I have spent on mods for my Pro now. When I look at and play it, it's worth every penny though. Here's what I have in my Pro to give you an idea of the types of mods you can put in a Pro to trick it out like a hotrod.
Aurich's trans/decals+Refinery custom interactive LED backboard
Zitt's pop caps
Warp Ramp Chase Lights
Vengeance Explosion mod
Vengeance visor/interactive led mod
Hallmark lighted Enterprise ship
Erak's Asteroid(5-piece set) mod
LED flipper buttons
LED speaker kit
FREDDY's ramp protectors