I would say that the aftermarket barrel is typically going to be superior (even the lower $ ones). However... that would depend on the PARTICULAR barrels being compared. The best Savage barrels (large heavy target barrels like on the LRPV or F/TR) will consistently be hard to beat. In any case, every maker of barrels will produce a dud - and conversely a "dream" barrel. So even an aftermarket barrel can "stink" (once in a while). That is where customer service will pay off.

I think either route you chose you won't be dissapointed. A build would be fun and you can get it just how you want it (and maybe for the right price too?) The BVSS is a great Savage and I have to imagine you'd be pleased with it as well.