I use an EMR II... and absolutely love it. I can only afford the one bag, and the EMR is a great all around bag. I use it almost every weekend, from hunting, to hiking with the family, to teaching Boy Scouts about backpacking, hiking, etc. It can compress down to a daypack that I can expand once I have an animal on the ground, and haul massive amounts of meat. I can use it on long, extended backpacking trips and strap all sorts of odd gear on it (bear cans, camp stuff, etc.)
I have never used the EMR II, but when choosing between the two, Aron did recommend that one. Many people don't like all the straps on the EMR (I do) so the AMR offers a lot of the same features, IE, can compress neatly, and expand with massive amounts of space, carries loads very well, etc. I think either way you're going to get a great pack. As others have said, check out the new Reckoning pack as well, as it has many of the best features from a number of their packs. Just my two cents.