After years of disagreeing with you, I've changed my mind. I think it is better to buy the DVD than to see the movie in the theater. There may be a few exceptions to this (VERY few), but let's just say that I've seen the light on the way out of the theater. My reasons are sixfold:
1) You spare yourself the double expense of seeing the thing in the theater, and then buying the DVD later.
2) You spare yourself the pain of sitting through nauseous commercials of products that you don't really want to watch, but which you're being brainwashed to THINK you want. (And c'mon: what a marketing ploy!)
3) You spare yourself the temptation of buying a five-gallon bucket of artery-clogging popcorn.
4) You spend your money on something you can share with others -- a DVD -- instead of something you can just talk about.
5) If you need to powder your nose in the middle of the DVD, you can just hit "pause," instead of waiting until the credits.
6) Your money goes to support the product you actually like, and not the moviehouse that's promoting what you like and what you abhor.
Here's a couple reasons why, even though I think it's better to watch a DVD at home than go to a theater, I might still go to a theater on occasion:
1) There's a movie that I really want to support so that the moviemaker makes a profit (e.g. The Passion of the Christ, Expelled)
2) I'm terrified of hearing spoilers and I can't bear the thought of wearing earplugs for 3 months.
3) My friends are going, and it's a fun event like going bowling.
So. Let me think about anything else we disagree on. It'll take a while, but I'll probably see the light on those things, too.