I own them both and I wouldn't want to part with either. TSPP is probably my favorite game of all time and the deep rule set is perfect for the home environment. It can be exhausting to play several games in a row on it but nothing compares to it when things start to click. There are just so many ways to play the game that it never gets old to me. I will never see everything it has to offer, and that keeps me coming back.
Spiderman has a much higher "just one more game" factor and it certainly flows better. Guests tend to like SM better because it's easier to understand and has a super high fun factor. The ruleset isn't nearly as deep as TSPP but the code feels very polished. I absolutely love the music and call outs.
Both are great games and they compliment each other nicely since they are so different. Both are easily top tier games but TSPP would be my pick by a narrow margin.