I currently own a Tron Pro and TAF, and my best friend owned a TZ for years - so I've got a lot of time on all three of these. They're all great games and iconic themes, so you really can't go wrong here. My thoughts are pretty similar to what others have said:

TAF
Get it if: you want a crowd-pleaser with good humor, middle-of-the road flow/speed, an easy-to-grasp rule set, and a game that's just plain fun.
Pass on it if: you want a game with a lot of depth that will take you a long time to see everything it has to offer.

TZ
Get it if: you want a game that's really deep and has a lot of shots/strategies, or if you like widebody pins.
Pass on it if: you don't like stop-and-go games, and would prefer a game that plays fast.

Tron
Get it if: you want a game that's fast, has great flow, awesome music/lights, is an adrenaline rush, and is easy to learn but difficult to master.
Pass on it if: you're looking for a game with humor, a lot of depth, and interactive toys.

I love all three of these, but for me, it would be a tossup between TAF and Tron. I love me some TZ, but it's just a little too on the slow side for me.