Stainless can be hot blued with the right set-up. However, the system is not too common among gunsmiths because of the extra cost for the tanks, burners, etc.

Black chrome is not too durable as I understand it, but I have no personal data. The following do black chrome

http://www.fordsguns.com/index2.htm
http://www.apwcogan.com/Refinishing%20prices.htm
http://techplate.com/firearms.htm also has a technical description of the coating.

OB