Have to agree with a prior post the Belz definitely have more variety and I think this is mainly because they carry alot of older products. The Premium outlet is much nicer and organized better. All in all the 1 Outlet at the Premium and 2 at Belz rule. I never knew about the outlets until I began reading this board. The outlets are a GREAT tip. I have read many people say the outlets carry older products, this is not entirely true. You will find merchandise that is currently sitting at the resorts and parks at full price in the outlets. The difference - the outlet price is 50% - 75% cheaper. There are still alot of 100 years of magic products at the Belz outlet, I didn't see anything except for 100 yr magic moment pins at the Premium. The outlet is a great place to take kids to find some cheap toys before hitting your first park.
Both outlets are on right of I-4 and both can be reached via International Drive if you like traffic lights. You can't walk to them from Disney property unless your crazy especially Belz. Premium is supposed to be 1.5 miles away from Disney Property but don't let that fool you. 1.5 down a highway.
If you get a chance I would definitely visit the outlets. We came home with some toys, plates, scattered mickey pillows, post cards, poster prints, etc.