I currently have both, and I prefer IJ to TSPP.

TSPP is a great game, but to get far into it requires a lot of time, and I don't often fire it up because when I do, I know I need to have 30 minutes or more set aside for a really killer game, and even with a killer game, I'm probably not going to ever see Super Mega Extreme Wizard Mode, or whatever it's called. Those long ball times also make it a game that my friends and I never play multiplayer on. TSPP just sits there in my gameroom, until I want a personal 1 on 1 challenge, then I fire it up once or twice a month. Out of all the games in my collection, it's always near or at the top of the "game I would sell first if I had to" list because of the long ball times and lack of multiplayer games.

IJ is not as deep (but it's no depth slouch), and the playfield can feel a little oddly "cut in half" as the pop bumper pit and rear of the playfield is only accessible from either loop or by deflecting out of the captive ball lane, which I purposely bank shot out of and into the pop bumper pit a lot for modes like super pops. I absolutely love the theme, art, sound, and modes though, as it really brings the IJ trilogy of the 80's to life in your gameroom. I absolutely loved that trilogy, so that's almost priceless to me. The tilting upper playfield is also a great toy if you have it tuned and operating nicely. You can also tune the mode start to negate a lot of criticisms about it through the use of drop dead foam, washers to lower the saucer, and aiming of the kick out lever. My saucer works amazingly well, and kicks to the left flipper for a cradle or drop catch consistently.

IJ is also a game that I've beat on a few occasions. Getting the billion points from hitting every switch in the game during the wizard mode is a thrill, and it's an attainable goal and not something I feel I'll never see like the TSPP wizard mode.

All that being said... you can't really lose with either of these games. Good luck choosing.