The AGA-T+ and the AGA-T2 were the same thing; at least, that was the impression I got. They were just referred to as different things.
The current revision of the AGA-T+/2 should be (at least I think) referred to as the AGA-T+ rev. 2. The difference between the two revisions are as follows: The first version came with a plastic polycarbonate tank, with a glass tank replacement that wasn't cut very well. The second version comes with a glass tank only with better cuts. (the IBTanked version is superior to both.) The first revision uses o-rings to create a seal between the glass tank and the end caps, the second version uses grommets. Personally, I feel like the first revision is better, because your liquid doesn't touch the o-rings and DOES touch the delrin grommets. I don't know if delrin will leach into harsh juices or not, I just prefer the o-ring style. (You can get o-rings that will fit the version two at a hardware store, or similar.)
Also, this may be an issue with my units only, but the top cap on the version one is much more secure than on the version two. I ordered a version two from DV just for a friend of mine to try, and his top cap is less secure. This can be remedied by wrapping some sewing thread or similar onto the top cap, before you slip the o-rings on.)