I'm somewhat picky. I can't stand watching SD videos / anything 480p or lower in quality. Usually, I'll go for whatever the highest quality is (provided it doesn't take up a ridiculous amount of space and kill my buffer). Most often I download 1080p, but if that's unavailable then 720p.
To me it depend on the movie. I dont download music clips, so that leave us just by the movie category.
So if it just for quick watch, like somebody recoment to me it, like some movie from 1996 with Clint Eastwood, dont care much about the kvality. But if it is blockbuster or a movie with hight rating I go for quality.