I am building a custom 308 AR.  I am going to have the barrel made, but I don't know if I want a LR308 or AR10 barrel extension.  I know that you have to run the BCG that matches your barrel.  What are the advantages of an armalite BCG vs a DPMS bcg?

Thanks.

DPMS is more common/readily available.  Many manufacturers support the DPMS barrel extension.  

Noveske is one of the last few to ONLY support AR10, and I suspect that will change soon.

Also, you can get some nice chrome plated BCGs from DPMS, JP and many others.  You get freaking ONE choice with Armalite - Armalite.  Sometimes hard to find individual parts, and during the SHTF politics of 2009, AR10 BCG parts were nowhere to be found, apparantly.

I went with an AR10 BCG because I just HAD to have a damn Noveske barrel on my 308 build.  Otherwise it would have been DPMS or similar.

And I can attest first hand the necessity of matching bolt/carrier/bbl ext. I bought a brand new chrome DPMS BCG for my Noveske / MEGA 308 build and the DPMS bolt would not lock with a round in my Noveske (AR10) chamber.
It also failed my headspacing gauges I bought.

Whoever tries to mix and match is a fool IMO.  Very dangerous.

Also ,I believe the firing pin, is a spring loaded design in the AR10 BCG. If that makes a difference to you.

Sho is.