If you prefer a deep story based ruleset I say Stranger Things, for points / tournament style play Avengers.

Personally I would go with a Stranger Things Pro and the UV light kit. Stranger Things Pro actually has a few things that move on it versus Avengers Pro that has very little. Stranger Things has the drop target bank, moving ramp and Demogorgon toy, all interact with the ball. With Avengers Pro you will get 3 drop targets and that's really it for toys. 3 drop targets for around $6k? Pass. Also the callouts on Avengers are terrible ("It's time to go binary"!) whereas Stranger Things has full assets from the first two seasons of the show + custom callouts by one of the actors.

In my opinion Stranger Things is the best pro for the money that Stern has put out in years, probably since Star Trek.