Upload & Sell: On
Last weekend I tried the Pro Messenger 180AW and the 200AW at my local camera store. As Lars said, the 180AW is taller, but I ended up going with the 200AW because I could see myself carrying more than the 180AW can handle. The 200AW is tall enough to fit a 1DMkIV with a 100-400 or a 70-200 f/2.8 mounted, standing on end. And there is still room for lenses and a flash on either side, plus a 7D with grip (but no lens) in the front pocket. The back zippered pocket of the 200AW is large enough for an iPad. The back pocket on the 180AW is tighter. You can get the iPad in there, but you can't zip it.
The problem with being able to carry all this stuff is weight. The shoulder pad is very good, but I don't see myself carrying the 200AW fully loaded very far. I didn't buy it for that, though. If I'm walking around I expect to have one body in my hand, and the bag just used to carry the lenses/flash/spare body (and I often don't need a spare body).
I also have a Stealth Reporter 400AW. That bag looks bigger than the Messenger, but it is boxy and rigid, and really doesn't carry as much as the 200AW.
One thing I really like about the messengers is they readily conform to your hip, especially if they are not stuffed full. That's not the case with the Stealth Reporter. Although if you have an iPad in that back pocket of the messenger, the bag isn't going to wrap around your hip at all.
My store had the 200AW for the regular price of $200. But Adorama and B&H both have it on special for $152. Interesting story - I asked my store if they could come down closer to the $152. I didn't expect them to match, I was willing to pay more for the convenience of being able to try out the bags before buying. But an extra $60 (including tax) was just too much. They actually offered to match the $152 "because I was nice about it and asked in a non-threatening way".
I haven't really used the 200AW yet, but I think I'm really going to like it.