Inductive hardening and conventional hardening perform the same basic function. Induction hardening is faster for production purposes and can be much less 'global' - it is possible to be selective about the surfaces to be heated rather than having to heat the entire component just to harden a specific area or region - like the ways on the base of a lathe. The process is more controllable and far faster than conventional heat treating and is considered to be a cleaner process with less or no scale.
The speed aspect of induction heating can actually be detrimental as many times a temperature soak required with conventional heating helps homogenize the grain structure of the material and can lead to a substantial reduction in work induced stress. A part that has been conventionally heat treated or hardened is typically less thermally stressed than a component that has been induction hardened - but this is, among other factors, material and shape dependant. Each process has a set of pros and cons - just like everything in engineering.
Scott
