I have a 14MM reverse cutter for AK's, and since the rifles usually group like shotgun patterns anyway, cutting the treads this way doesn't seem to be a problem.
But on the other hand, when your taking about AR barrels, you would want something a little better to maintain the bore consistency that just the pilot used on the hand threaders.
Most of the Dyna kits run around $70, which is the same price as Kurt charges to cut, thread, and crown two barrels. Granted the Dyna kit may be cheaper if you have more than a few barrel to thread, it's just that you take the chance of compressing the most important last inch of the bore on the barrel using the hand threader. If you don't mind the barrel grouping larger by an inch or two, then the Dyna kit may be the way to go (you still may have to turn the end of barrel to get the OD correct for the threading).