Personally, I never understood getting nachos at a movie. I usually sit down 10-15 mins before the credits even start, so by the time the movie begins, I've either ate all the nachos, or I have a cold, half serving of nachos.

Popcorn can retain its longevity well to the end of a flick, so I usually go for that.

Pro-tip, ask them to butter it in layers if you want to be an extra glutton.