mos0321recon
Here's my 2 cents.
I would recommend the CA M249. If you look in the add section, there always seem to be a lot more A&K M249 for sale than CA. To me, I interpret this as owners of CA M249 are much more satisfied with their guns.
I've also been able to compare a CA & A&K side by side and you can definitely see that CA is a better quality gun.
Also, it's a heavy gun. So you better start masturbating a lot to build up your cardio and the muscles in your arm so you can carry that bad boy.

While your at it. Invest in a wide padded sling such as a Vickers SAW sling. A good padded sling will greatly reduce your fatigue.
Another thing that I would recommend is that you don't stick a big battery in your box mag to power your gun. If your box mag goes down so does your gun. I prefer to keep the battery in the gun so that I can switch to another box mag or Hi-Cap mag should it crap out on you for any reason.
On the subject of box mags. Nut sacks allow you to hold and maneuver the gun more easily because of it's smaller size. It's also a little bit more lighter because of it's smaller size. Pharaoh 6 gave an excellent review between the CA and MAG versions. Personally I like the auto winding versions. However, I have not used the CA nut sack so I can't speak about it's reliability. I do have the A&K large box mag with the sound activated auto winder and it works very well.
One other thing to consider is the amount of BBs that you are carrying in your box mag. Remember, the more you carry the heavier your gun will be. If I know I will be doing a long patrol, I will put only 1,500 BBs max to reduce weight. In 90% of your engagements, a single fire fight will finish before you need to reload (Unless you have Hi-Speed gears). But if I know that I will be in a defensive position, then I usually fill up.
Last, before you go buy one. See if you can borrow one first before you buy. Lugging a SAW around is not for everyone. You're usually slower and not as maneuverable as everyone else. And the weight gets to some people after a while. But when the shit hits the fan in a target rich environment. You're usually the one with the biggest grin on your face.

If you can't borrow one. Maybe an A&K M249 might be a better choice to start with. If you really like it after a while, then I would upgrade to a CA.
Here is my M249 as it has evolved.
Original Configuration
Mk-46 MOD-0
First Upgrade
M249 Mk-46 MOD-1
Current Configuration
M249 Mk-46 MOD-2
