My understanding is that the hardening process used on the cam lobes surface is better on a billet cam than on a regrind. While I could not find a definitive statement regarding this difference, here are some term definitions from Tighe Cams which will help demonstrate the difference.

Billet Cam: This is the term for a camshaft made from a solid piece of cast iron or steel bar. 99% of steel camshafts are made this way.

Regrind: Term used when a worn camshaft is reprofiled to the same profile or modified to a different profile. To achieve this the bulk of the shaft may need undercutting to keep the base circle above the shaft diameter.

Rockwell Hardness: The type of hardness testing used to check the hardness of most hardened materials. Rockwell C process uses 120deg diamond with a weight of 150kg. of preload on it. This is loaded into material, and depth of the indent is measured . The result of this is given in a Rockwell C measurement.

Flame Hardening: This is a hardening technique using oxy/acetylene torch to heat a camshaft to a cherry red which is then quenched in a water based coolant.

Induction Hardening: An electrical process of heat treating, where a camshaft is passed through a coil, through which a high frequency current is passed. The camshaft inside the coil is quickly heated to a cherry red and quenched in oil. Ivan Tighe Engineering hardens all new camshafts using this process.

Here's the source of the above: http://www.tighecams.com.au/camtypes.htm

 

Thats the best definition I have seen to date IMO.

 

Thanks for the information, that is very enlightening.