I hate long shorts. I have good quads but nobody can see them. I think this fashion of long baggy shorts was started by pretty boys that do nothing but bench and curl and never go near the squat rack.
At the gym they range from the top of the knee to below it.
Casual wear they are middle of the knee.
* I don't like short shorts. Too long is stupid too!
My workout shorts are an inch below my knees. I feel more comfortable as such though I admit that they are rather not practical when doing squats. The problem with short shorts are that it just wraps around your glutes/quads and looking ridiculously tight.
Casually speaking I rarely wear shorts, at least pants of some light material is better than shorts.