So after I ordered the Saddlemen tail bag I saw another similar bag for quite a bit cheaper. This one is the Gears Canada Navigator tail bag.
http://www.amazon.com/Gears-Canada-N...ilpage_o01_s00
It is supposed to be 52 liters just like the Saddlemen, but it sits lower and is longer. The drop down portion on the sides are not part of the main pocket, but separate compartments that are accessed via a zipper on the side. I do like the mounting straps better, and there is an extra velcro strap on the bottom of the bag that you can wrap under the seat. It also has a built in rain cover.
I think the Saddlemen bag is easier to pack and has more usable space, but the Gears Canada looks better and more streamlined. The Saddlemen looks like it will be easier to strap other stuff on top like a tent, but the Gears Canada has some bungy webbing to attach loose stuff with.
I'm going to keep them both and use the Saddlemen on my bike and the Gears Canada on my daughters bike as we go on some weekend trips this summer.
I'll try to do a better comparison article in the future when we actually load them up for a trip.
Gears Canada on the Left and Saddlemen on the right.