While I can enjoy both as a spectator, as far as involvement goes, I'd definitely say film. With theater, on or off stage, you're under a lot of pressure to make sure everything is 100% perfect for that live performance, because the slightest mistake can have dire consequences. I remember in Grade 8, I was part of the stage crew for our school's big year-end musicale, and I got in big trouble with the teachers one rehersal night, all because I had a bathroom emergency; apparently, they found it irresponsible that I had to run to the bathroom for a minute, and even threatened to relieve me of my duty if I did something like that again . . . I guess my only other option would have been to just crap myself.
But theater can be fun to enjoy as a spectator, and more often than not, live performances are always better live, in-person, as opposed to televised or documented.