Quoted from PanzerFreak:I own both STTNG and a ST Pro for some reason, lol, probably because I enjoy Star Trek so much. STTNG is definitely the more loaded game and is a blast to play. However, I would give Sterns ST the edge when it comes to rules as it has a far deeper ruleset then STTNG in my opinion. With the official movie soundtrack added to Sterns ST it really makes the game one heck of an adrenaline rush.
Star Trek: The Next Generation is a pinball machine from 1993
Star Trek (Pro) is a pinball machine from October 2013
Considering the 20 year technology gap you would expect the Stern version to have a deeper ruleset.
The fact that the Williams version is still the more desirable version would lead to higher prices.