The Admin Pocket will have more capacity and more organization than the Aston Pocket. The Aston Pocket is the slimmest pocket option and good if you need just a little organization and not too much additional capacity. The Aston Pocket comes with a different compression system than the Umlindi. You will completely replace the compression straps on the Umlindi with the straps that come with the Aston Pocket.

The Admin Pocket will integrate with the compression straps that come with the Umlindi. It can also be turned into it's own little daypack, with the addition of the V2 Pocket Harness. 

I've had the Pals Pocket and now the Admin Pocket on my Umlindi. Hands down, the Admin Pocket for me! The Pals Pocket was nice but the lack of built in organization always had me looking for pouches to velcro or molle in and that added bulk and weight.