The main difference is that with Artsicle you get the original, one of a kind piece where as with TurningArt you get a reproduction of a work. It's just a different approach. On TurningArt you may find some more familiar names where as with Artsicle we're focused on emerging artists before they get their break.
+1 for turning art, an awesome service with some great people behind it. I find that product a lot more appealing than renting/shipping originals without a purchase.