I own both. Here's my assessment:

T2: Great game. There is a reason they made over 15000 of them. The super jackpot is very fun and rewarding. It may be my penchant for sci-fi movies , but I LOVE the call outs. The flow is fantastic, and I love the artwork/look of it. If you are looking for a quick, straight forward game...it's a great choice. I actually originally bought it as a "filler" pin that I figured I would trade or sell quickly...but it has now lasted for years in my collection. It definitely has that 'one more gane' feel. I should also note is a one of the top machines for mod add-ons.

STTNG: It has one of the best theme integrations of all time. There are tons of shots and the game is packed. Full cast call outs are great! I enjoy the art, and it is a pretty deep game for the era. The outlanes can be tough, and a lot of people complain about issues with it needing more fixes than a lot of other games. It is widely considered one of the top games ever made.

Final thoughts: If you are able to get both, I would recommend doing it. In spite of both being made by the same company, in the same time period, and both being sci-fi themed...they almost couldn't be more different in terms of gameplay. They give a great changeup to one another.

If you can only get one, you need to decide if you like more gadgets or more flow, which theme you prefer, and how deep of a pin you are looking for. Only you can answer that. If money is a consideration, STTNG also costs about 2k more. If all things are equal and the money isn't a factor, I would choose STTNG.