Top 3:
The Variegated - If you have a petco near you I would highly recommend checking to see if they have the Pincushion (Variegated) urchin. If you do see some hopefully they are healthy and doing well. I only paid $12 for mine, and there is a 30 day 'warranty' if they die. But after I acclimated mine and added him was moving around like crazy, and flawlessly acclimated to my tank. I have had him for almost a month.
Tuxedo - They are usually pretty easy. You can buy a captive bred one online since stores usually do not seem to carry captive bred ones for some reason. I think they may be more sensitive to higher nitrate, and should be acclimated really well to ensure they do well.
Shortspine/Rock Urchin - If you see one of these in a store I would highly recommend it!! They are super good! They will clean mostly the rocks, and pretty much scrape it down completely. It is insane. They'll also happily munch on any other algae on the rocks, and glass if they come across it. I like this service since they are helping give the rock space for the beneficial bacteria colonize by removing the algae.