I generally won't buy unless I've seen a trailer or two. Sometimes reviews help sway me. And reading opinions posted here can help. I'm not too big on movies anyway.
But I certainly prefer to buy a BD, or maybe rent one (haven't done that yet), to going to a theater. And that, for a movie I might only watch once. Fuel, tickets, god forbid- snacks, all add up quickly and can exceed the cost of the BD. Plus, I think my audio system is better than a lot of theaters. And the usual (house is cleaner, no talking teenies, no cells going off, etc).
Old topic, but let's beat it to death again. Most tickets $8-$12 @. Or a junky theater with poor sound and older titles for $4@. Figure $16-$24 for tickets for two. Figure another $3 or so for fuel. So before you eat anything, you're out $20-$30 plus a little wear and tear on your car. I can buy a BD for that - or even less. It's cheaper to buy a BD online than to take two people to the theater.
Of course, I also rarely pay full price for a title. Lot's of sales still. I'm up to about 80 titles, about half of which I haven't seen yet.
But to touch on the question, I suppose I should have picked "other" in retrospect. The main reason I'd buy/see a movie is because it's a book I read and enjoyed, or part of the Star Wars franchise, or certain other already known quantities. Or a BD version of an old classic I enjoyed, like Casablanca.