I have 2 DPMS B/C units one chromed, one not.
I don't experience any difference in the rifle with the chromed bolt.
Chrome material is "slicker" (lubricity) than most metals, tolerance the same, a chromed bore will exhibit less friction on a bullet vs a moly bore. With a target grade lapped barrel the difference probably will fall in favor of the lapped barrel.
With that in mind, the chromed bolt might wear less over time on the upper rcvr, however it is also a much harder material so any wear will favor the upper rcvr and not the bolt itself.
In all reality, I don't think it matters.
As far as cleanliness, ammo with a quality powder will make the biggest difference.
Outside of his hype, I don't think you'll go wrong with the DPMS product. I have a AR-15 lower and a upper from DPMS with zero complaints. The DPMS upper has received a far greater "beating" than any other upper I have.
Here is a tip: Secure the buffer tube and keep it fom backing out with temporary loc-tite.