Since both machining modes shown above operate a substitution of real expected surface with something different ( an arc in case of continous mode, and a plane in multi-cut mode) some form errors occour.

This means that gears milling may be used without problems ONLY in case of further grinding (expecially for multi-plane machining mode) or in case of low-quality gears, for which continous mode milling might be satisfying enough.

But don't forget that also hobbing has quite the same problems, since a good hob in AA class may be built only in brazed-blade mode, needs a proper sharpening, and its quality depends upon re-sharpening process too, while indexable insert hobs hardly reach quality A and often stop at B.

Gears milling is then a comparable alternative to hobbing, just because both process might lead to a comparable quality.