The three most common twist rates for the .308 are;
1:10
1:11.25
1:12
Normally you would choose one that matched the range of bullet weight you expected to shoot. Lighter bullets get looser twist to reduce pressure/friction, heavies get tight twist to maintain stability.
That being said, after having a long conversation with Mike Dagerness from PROOF Research (formerly Jensen Precision) he basically advised that if you are buying a top quality barrel, get the tightest twist you can. Recognizing that this guy makes his bread and butter manufacturing HIGH end barrels for all manners of shooters, I respect his expertise.
Buy quality, stick with 1:10, shoot whatever you want through it.
I have a 17", carbon fiber wrapped, stainless steel, Satern match barrel, with rifle length gas and a 1:10 twist.