I would say it depends on what you want to do with it...
For myself, I would get the Bushmaster if you want a lite, easy to carry gun that you can blast the heck out of. Bushmaster has a great barrel and I would highly recommend it.
In the same breath, if your looking for the bull barrel look and a little more accuracy, I would suggest the DPMS bull barrel. I have a 24" from them and it shoots so good it is scary!!! But these barrels aren't really made to be heated up under rapid fire.
I own both of these company's uppers and recommend them both, it just depends on what you want to do with them...
One more side note, when people pick up my bull barrel, the first thing that comes out of their mouth is..."boy thats heavy!" On the other hand, before the lift, they say, "that is one cool looking rifle!"
Good luck,
fuatos