There is a lot to be said about router bits but let's focus on performance. Finish The finish, in this instance, is the finish imparted to the work. The best of finishes are chatter free without burns or tearout, smooth and need little sanding.
Many variables influence the quality of the finish.
Control of these variables improves cut quality and safety. The second most important area of concern is probably cutter life and economics. We've all heard that the industry standard for woodworking bit material is tungsten carbide and it's supposed to last 6 - 10 times longer than high speed steel. However, you might be surprised to learn that even at 10 times the life, carbide deteriorates rapidly. That's just 10 or 12 trips around a 4 x 8 sheet of ply.