Ok, I am looking at finally getting the barrels for both my upper builds now.  They will go on a glock mag lower and I am looking for something in the 7.5" size space.

Looking around at barrels, there seems to be less differences between pistol barrels and 5.56 barrels.  From what I can see almost all are made of the same material, all are button rifled, use the same twist rates, same crown angle, etc.  

Is there any barrel that is better than others?

Any to stay away from?

Are you planning blowback or DI for your builds?

Blowback, already have the buffer and stock (9mm pdw style)

Never seen di 9mm stuff actually

DI 9mm is around, I had Ron Williams with RMW XTREME build me a 10.5" DI 9mm a couple months ago and had a chance to run some handloads thru it last Friday and it shot great. Would have loved to get some groups but it was very windy so just shot steel @ 50yds. It was a blast. One thing with DI 9mm it is a handload only deal, I ran some factory 9mm 124gr blazer thru it and had to clean it to keep shooting. I also have a RMW XTREME DI 40 S&W that runs like a sewing machine and is very accurate.

The feed ramps are the most important difference, that's also the biggest variable among different 9mm barrels that I have seen.