Having built well over 350 guns, I view barrels from several different aspects. As Rich said availability is important as is price. Colerain has been my top supplier for quite a number of years, and delivery is usually spot on. Rice barrels makes a wide variety of profiles and this is where I go when I need a specialty production barrel. The exterior of a Rice barrel is nicer than Colerain, but there is a price for that nice finish. When I need a truly custom barrel Ed Rayl is the go to guy. There isn't much that he can not make and at a reasonable price.
Accuracy, I have not had any barrel that would not shoot acceptable groups. I shoot and adjust the sights on every gun I build. Obviously, I do not have time to get into load development as Daryl does, but using pretty standard loads i.e. like 70 gr,3f, 490 ball and .015 patch in a 50 cal. all have printed nice groups. Some have shot tighter than others, but then I might have been having a good day. I have heard some blast Colerain's barrels, but I have clients who have awards from Friendship competition that were shot using Colerain barrels. The barrel makers like the rest of us are trying to put the best product out at a competitive price as they can. All are good, some individual barrels may be better than others. Remember Winchester made a big deal out of their 1 in1000 promotions so even in their barrels some were better than others.
Ron