Memory Maker: cost - $149 in advance, $199 in the parks.
You go to the same PhotoPass photographers, take the same photos, etc. You link ride photos + meet & greet/character meal photos (like from Cinderella's Royal Table) to your Memory Maker account. When you get home from your trip, you can do the same "creative" changes to the photos, like adding borders and signatures and such. You download all your photos - they're available for 30 days, I think? You can download them multiple times over those days, burn them to disc, store them on a flash drive, back them up into the cloud, print them anywhere you want, etc. You can spend a bit extra (I think $30?) to order all your images on CD.
PhotoPass: cost - $119 in advance.
Same process during your trip, as far as taking photos. Your ride and special meet & greet photos are NOT included in the cost. You get a cd of your photos included in the cost, but any prints you order separately (say, of ride photos or character meets), cost $15 apiece. If you choose to order a few of those, it adds up fast. If you don't, then the savings is nice.