Ok my answer is going to be a little disappointing, but I thought about it for a bit and here's what I can say...

Usually I read a book or I watch a film, I don't think I've ever done both for the same story. Sometimes there is no equivalent book or film, and when there is, I personally just end up choosing whatever format my gut says to try.

If I've imagined a universe and story in my mind (from a book), or had the experience delivered to me (in a film), I don't want them to conflict so I just choose one. Probably because I see so many debates about this online and I'm just like, "nah I'm not getting involved".

I'm actually probably the worst qualified person to give an opinion on that!! But I recognize I'm probably a weirdo, as I don't even watch film trailers or read the synopsis of books before I read/watch them. I just kinda hear about it however that happens, and decide to either skip or jump in. The exception to this being non-fiction or educational stuff, then it matters a bit more.

I guess, I just wanna enjoy (or dislike) a story and leave it at that.

Sorry for the total non-answer. But now you've got me curious, what's your answer? Maybe I'll make an exception for Grandwolf319 haha