In reply to Daniel:
Firstly, what are you missing from your current kit and why do you need more? These kits seem to be little more than a collection of bandages and some antiseptic. If that's what you need could you not just buy some more bandages in stick them in your existing bag? They don't even have moleskins or compeeds, which should be a very basic part of a kit.
My take on these kits is to get the one with the best *container* as you will probably end up replacing most of the contents over time anyway, either through useage or expiry of medicines. Make sure everything inside is easy to see and easy to access- IMO a bag like this (which I have) is very convenient to use though overly comprehensive for UK conditions:
http://www.campmor.com/webapp/commerce/command/ProductDisplay?prrfnbr=1095&...
My flatmate has an old lifesystems bag that doesn't have a zipper on one of it's compartments. As a result, if opened incorrectly it sprays plasters everywhere.