Internally (mechanically) both of those guns should be identical (King Arms version 2 gearbox and parts). The only real differences are the externals. The CQB version being better for tight quarters and the carbine version being more of a multi role weapon. The Carbine length weapon is a hybrid in between a full length battle rifle (M16 for use in long distance engagements) and a shorter barrelled weapon good for CQB combat. The idea is that the carbine is good for both applications but doesn't excel at either.
The other main difference is that the CQB version has no onboard battery storage, it's "wired to the front" and will require you to use a peq box to conceal the battery. The carbine version is "wired to the rear" and will allow you to stow your battery in the butt stock.
Last edited by Kozzie; May 21st, 2012 at 02:20..