I was in your spot too about a month or so ago, I went with the 511 because there are 3 bags built the same way, the midway one, the cedhk one and the 511. I know you can get the 511 in EDM at milarm's and there is another shop out in spruce grove. You can also get it for 109.00 from basspro when they have them in stock, other wise 149.99. Once you factor in the shipping and dollar exchange sometimes buying local is better... Plus you get to take it home right then. I do like the way that eberlestock bag looks too though. Going to have to see what it is all about.
Oh and my load out in that 511 is 2 pistols ammo, eye's, ears, full pistol mag load, FAK, paperwork, holster... and cleaning kit. I think ... LOL might be more in there but I still have room in any case. The nice thing is that the inside comes out and there is enough room beside it that you can store your pistol in a case locked up with out any issue. If you want I can take some pic's and show you what I mean if your interested in the 511.
Peace