Well Dave, I'll try, since you lowered your standards to "anyone."
I believe that most of the parts suppliers like RRA, DPMS, the kit companies, as well as Bushmaster, Armalite etc. all use Wilson barrels. I think that only OlyArms and Colt actually make their own.
The only big feature difference is whether they come chrome-lined or not. I believe Bushy and Colts are chromed, the rest aren't except by special order (tho I think RRA makes a M4 that's chromed.)
One might find Q/A checks could differ from one supplier to another and catch a quality problem here or there. but I don't read many complaints about barrels around here.
Except for high-end target barrels, there's prolly not much difference between 'em, again, mostly because they come from one source.
[Maybe some hot-head with an axe to grind will flame me on this and you'll get the [b]REAL[/b] answer!]
C_M