By and large, Smartparts makes some pretty nifty barrels. As far as I know, the DAC barrels are quality too (never tried one, so I can't speak from experience on that one).
My advice is to use both. Depending on the paint you're using, you have to make a choice. See how the paint matches up to the barrel. Drop a paintball into the barrel, and see how it fits. If the ball rolls right on through out the otherside, the fit is not as it should be. If you have a hard time getting the ball in, you're going to end up with paint soup. The ball should fit in the barrel easily, but kind of snug, so that you could easily blow the ball out of the barrel by puttiong the barrel to your lips.
Also, which barrel you use, if they turn out to be the same bore (diameter), is depending on the field you're playing. Obviously, if it's a field that's 'crowded' with obstacles, you might want to go for the shortest barrel, because it'll give you somewhat more agility if you're not constantly busy detangling your barrel from dense bushes or whatever. When playing Sup'air or suchlike, it doesn't really matter. Although the longer barrel may give you a bit more accuracy.
Have fun!!
