I am starting to keep my eyes out at several LRS and TE for running shorts sales for the coming season. I will only get a couple pair, the tights I wear at the gym don't have any pockets and I want something just for trail running.

The reason might be obvious to everyone else, but WHY are running shorts so....well...SHORT? Is it to prevent chafing? Better ventilation? Currently I am thinking of something like this at Trail Runner Sports. They are longer, have pockets, and won't break the bank. I am thinking that something for the trails should be a little longer. There is a reason I hit the mountain bike trails last year with a pair of clippers to cut back the thorn bushes

I see that TE sells these longer compression running shorts for warm weather. They are rather outside my budget - and they don't currently have my size anyway. Is there an advantage to compression running shorts, especially for the older, novice runner?

Just looking for tips on what to look for, I've a stack of cycling shorts that I wasted a good amount of money on because I didn't know what to look for. I am only researching now, trying to do my homework to avoid possible impulse buys. I am too good at those, and I only want to buy two pair. I think several of my cycling jerseys and some of my more general technical fitness tops will do for now.