Quoted from waspinat0r:time in on tpa and vp.
stick with Visual pinball, TPA is ok but the physics are meh. at least in VP you can tweak the physics you don't agree with. its free and there is currently a bigger selection of tables being supported by a passionate community. The main thing TPA has going is it's much easier to get setup and you don't have to keep updating to get the latest and greatest.( probably does it for you)
The biggest issue with Virtual pinball as a whole is nudging. Still better then nothing, its probably one of the main reasons I'm in the hobby. You can get by with a cheap computer and play via keyboard, but it's obviously better setup in a cab. I mainly use it now to try to better understand rules to games.
not sure if they were listed yet, here are the main four sites the content comes from.
http://www.monsterbashpincab.com/ (new tables not listed elsewhere from really good authors)
http://www.vpforums.org/ (been around the longest, doesn't have modern sterns)
http://vpuniverse.com/ (lot of backglass dwlds, and has the latest sam pinmame to play sterns)
http://vpinball.com/ (This one is probably the best with the most content)
at any rate good luck.