Hey, Mustang...
First, don't get a muzzle break. 223 doesn't kick that much and just makes it *loud* for your fellow shooters at the range - and a bare muzzle will be more accurate anyway.
I would buy the Bushmaster simply because it has a chrome-lined barrel with a milspec chamber, and its receivers are made from forgings.
You won't have - or will have far fewer - feed problems, etc. w/various types of ammo with a milspec chamber and chrome lining. The largest percentage of folks posting to these boards and "the list" that complain of extraction/ ejection problems have rifles w/unlined barrels and chambers set up for SAAMI ammo specs. [For the record, I've had a J&T kit with an unlined barrel that worked just great. But from now on, knowing what I know, I will always get a milspec chrome-lined barrel from the "ABC" guys (Armalite, Bushmaster, or Colt).] The lined barrels are *much* much easier to clean and last far longer due to chrome's hardness and wear resistance.
At some point, I believe DPMS only offered upper/lower receivers made from castings. They may now offer forgings, I dunno. Castings are more fragile (i.e, crackable) than forgings.
Being in Kaliforna before our AW bans set in,
I had to buy stuff that would last for a lifetime.
I have, again for the record, not heard of many problems w/DPMS. But they sell far fewer rifles, it seems, than Bushmaster. While I've heard of the odd Bushy issue, most folks seem happy with 'em. I have Bushy, Colt, Armalite and J&T and have had no problems; I'm particularly fond of my Bushy Dissipator upper on a Colt postban lower; it's my go-to gun.
The price difference from a chromed vs. unlined barrel and from forged vs cast rcvrs may well be over $100 or so.
The "bull barrel" will, on average, not be any more or less accurate than a std. profile Bushy barrel, and your AR will be a helluva lot easier to carry around (over the hills & thru the woods, etc.) without that extra 1lb (?) of metal.
If you intend to use a scope, I'd recommend you get a flat-top model (for either brand).
Bottom line: you won't go wrong with a flat-top Bushy. Get a carry handle for iron sights too; if your scope fails you can put the carry handle back on and be pretty close to zero.
Regards, Bill
-Bill Wiese
-San Mateo, CA