In terms of value, TSPP is always going to be desirable. Most of the new stern games as of late tend to take a hit in value on the secondary market. At the same time, the prices on classic games keep creeping up.
In terms of fun, it's hard to say yet if GOTG is going to have staying power or not. From what I've seen, it seems like it's fairly repetitious. Also, from what I've heard, it's been mediocre on location.
I like the theme and the layout is somewhat interesting, but if it were me, I'd probably hang onto TSPP unless you really find yourself not liking it any more.