BRILEY has an excellent reputation in the shotgun world, and I believe that the build their chokes with the correct conical/parallel concept in mind. I DO believe that from a VERY picky stand point[I'm a sporting clay competitor] that Briley's QC is not the best as far as tolerance[+/-"]. I prefer chokes from SEMINOLE GUNWORKS[800-980-3344] www.seminolegun.com
. SEMINOLES chokes are biult to exacting specifications from the best materials. I've always been VERY HAPPY with all thier work.
That being said, almost any of the quality aftermarket chokes offer increased performance over the factory tubes. The real key to great performance is to have the chokes made for your EXACT bore diameter, which is what SEMINOLE will do for you. Shotgun bores can vary from gun to gun considerably. .010" variance is not uncommon, that is the difference between improved cylinder and modified! Moreover, the transition of shotcharge from bore to choke can be hindered and 'upset' if the choke and bore transition don't matchup.
Sorry for the long post, probally more info than you wanted. The short and skinny is, Briley's are good, IMHO SEMINOLE is BETTER.