I guess I'll be the first to say I favor BCM.
However I will say when it comes to barrels, the DD probably has a slight advantage In accuracy.
All other components are even. BCM has never let me down in parts or service. I tend to piece my AR's together a piece at a time. My latest rifle uses BCM's 14.5" barrel, Mod 1 compensator, gas block, Gunfighter ambi-charging handle, and 13" KMR rail.
I have been through DD's Omega and lite rails and while the quality was there, they just didn't do it for me. Also had a DD BCG and while quality was above par, I decided to go a different direction.
Nothing against DD, they are great rifles and parts, but BCM for me has been great and then some. Also I gave them a few extra brownie points since their owner is a fellow Leatherneck and they put out quality/well thought out parts with great service. I personally cannot say enough great things about BCM.