I prefer shows. I've been to a lot of clinics where the other participants were the worst snobby, whiney, show-offs that ever walked the land. At least at a show I don't have to put up with a clinician focusing all their time on these people, probably because I actually do my homework before going to a clinic. I generally get pushed to the side because my horse isn't a homicidal maniac. At least, that's how the western-oriented or natural horsemanship clinics in our area go.
Showing is like "me time". Once I get into the groove, I really like the personal time to myself and my horse. And when your in upper level shows you get to be around other people who are really professional, and their horses who are well-trained. The atmosphere is very "zen" and you don't have to worry about getting mauled by someone's rank animal they pulled out of the pasture and decided to try and do a clinic with.
But, I digress, haha.