TNA for sure. I plan on making it my first nib game. Over the years, I've really become fond of late 70's/early 80's solid state titles. To me, that was the golden age of pinball. Fast games with awesome designs and art, but without too much else tacked-on (like non-interactive toys, video/dmd displays, etc). Yes, tna has an lcd, but it also has digital displays for the scores, and the lcd isn't a big focal point of the game.
To me, TNA is the future of that era of pinball. It *is* all about the action on playfield. The rules are fairly simple, but to actually beat the game is devilishly difficult. Beyond that, Scott actually created the soundtrack for the game (and it's amazing!), and has been actively working on bug fixes and new features (co-op and vs. co-op? Nobody else is doing that!)
Build quality is excellent. I'll admit to being a fan of Spooky, but that only happened after following the development of TNA over the past couple years. If anyone deserves our nib pinball $, I'd be hard-pressed to find a better candidate.
Good luck whatever you choose, but if you *actually* want a game that's different, i think the choice is clear. SS is fun, no doubt. I'd like to get one someday bc it's a crowd-pleaser and an awesome game visually (and climbing the stiff-o-meter is a rush!)...But in terms of overall gameplay, TNA will hold my interest far longer. Plus i think TNA will prove itself to be one of the more enjoyable multiplayer games, to boot. Good luck! Ain't it nice to be in a position to choose between 2 awesome games?