Quality of manufacture is what sets them apart. Old style glue-ons were pretty iffy. The newer push in styles are much better in consistency. Most are made to certain standards so that the throat size is pretty consistent from nock to nock and often from one manufacturer to another. However not all fit the string the same. That's one reason why there are different diameters of serving material. They also line up perfectly with the shaft unless you just happen to get a bad nock, which is rare. They can be indexed to give fletching clearance with a conventional rest. Frankly, with so many good reason for them I just cannot see any use for glue-on nocks any more unless you're a true traditional shooter.

After many years of shooting I have come to the conclusion that Easton's G nocks are about as consistent as you can get. They compare nicely to many of the nocks made for target shooting like Beiter.