[seabass]

There is a negligible difference between the cqb and the full sized M4. If you don't play cqb I would just pick whichever you like more.

The DTT pmags come with vanaras internals. There not as good as the systema ones. You might have some troubles with em. I have 12 and I find myself constantly tapping the bolt release.
From what I've heard the 2012 motors are worst than the old ones. You might be better off to get an FCC 2.5 motor or complete ptw.
The hopup mod is absolutly necessary, get it done or buy an aeg.

If your a semi auto guy I highly reccomend a ptw. Your never gonna find the same trigger response. But if your a full auto guy save yourself some headaches and a huge repair bill and get bob at bent barrel Airsoft to mod your aeg.

Hope this helps cheers