I am a TSPP owner, so biased, but TSPP all day long because the ruleset is *very* deep. Check out the attached chart I made to help wrap my head around the major parts of the ruleset (there's even more that's not shown here). I've had it for about 4 months and still have yet to have a game where I got more than 2 of the goals needed for the final wizard mode.
Don't get me wrong, I really like Funhouse and - in general - prefer System 11 and WPC era pins to many modern pins. But, if you're looking for a game to keep for the long haul, to me it's no contest.TSPP Rules v3 (resized).jpg