I haven't bought any for years until the huge number of amazing rookies this year got me interested and I have been wondering the same thing. It's pretty much only Upper Deck this year who have a few different sets, picking between them is mostly personal preference - excepting that they have a couple cheaper mass produced sets for kids at the corner store like MVP.
Ebay is a great place to look around and get an idea of value, or beckett magazine online has good breakdowns of the various products this year on their hockey site.
http://www.beckett.com/becketthockey/default.osi
on the left under previews and breakdowns there is some good info