Firstly I have to admit that I'm a SRP fan. However, to even it out, I've been more a TAF theme fan than a SM fan.
I was considering getting a TAF and found a place to spend some time on one. While the callouts are fun, I found them to get too old too quick. That's not to say there isn't repetition with SM, but if you're playing it "right" you have a greater selection of callouts.
Ritchie is the king of flow and one thing I really like about SM is that even with the ball capture it has, you can (or not) bypass any capture with a double-flipper (i.e., releasing the ball immediately). This give some great flexibility in how I want to play it - whether its strategic during multiballs (let the capture linger) or wild (I want the ball back ASAP).
I found both to have really challenging and rewarding shots (and combos) when you want to play your best game. Where I really found the difference is when I just wanted to walk up and play a casual game. TAF still requires good shots to make things happen while SM I can get great flow and a fun game when I walk up to it just to kick a ball around or while my mind might actually be on other things (I'm the type that does his best thinking while the mind is half occupied). In this respect I think SM gives better flexibility of play - tough to get thru all the modes (only been to super hero a couple times) when I want to concentrate on playing pin, yet I can come back to it over and over still really enjoy the casual games. I think this also extends to those who may not have exposure to pins - they tend to gravitate to the SM because you can have fun rewarding games with limited knowledge of the rules.