The Bushmaster is 98% the same as a DPMS LR308. Major differences are the (useless) flip-down trigger guard and the somewhat beneficial midlength gas system. (In a 5.56 midlength gas is the way to go, but it has far less benefit in a .308.)
The Armalite is probably somewhat higher quality, but there are still plenty of problem reports from owners. My 2 cents is this:
-for a really high quality .308 AR, I would look at the LMT, upcoming Colt SP901, Larue OBR and Predatar 7.62, and the Noveske. Of those all but the Noveske use the original AR-10 / KAC SR-25 / DPMS pattern mags, which are easier to find and cost less.
-For something that costs under $2000, I would get a DPMS LR-308 for $900-1000 and have money left over for whatever you want. IMHO there is a smaller difference in quality from the DPMS to the Armalite than there is from either one to the group listed above. And the DPMS is plenty good for most hunting and target shooting uses.