I have to contradict the quote: "There are only two kinds of stainless steel and they are both far superior in strength and toughness compared to the hardened steel bolts."

I assume you're referring to 300 series stainless (303, 304, 316, etc) which are commonly used in fasteners. These are roughly equivalent to Grade 2 bolt strength. There are many other varieties of stainless but not commonly found in fasteners.

300 series stainless is FAR weaker than Grade 8 hardened steel bolts. 304L SS, for example, has a yield strength of 30 ksi. Use these to hold heavily loaded parts together and you'll regret it.

Grade 8 bolts per SAE J429 have a minimum yield strength of 130 ksi. I have yet to see a Grade 8 bolt fail in automotive service.

Totally Stainless is aware of this disparity as you can see at this link:
http://totallystainless.net/yoursafety.htm

"Unleass you have a death wish, don't bolt your brake system/suspension together with regular strength stainless steel fasteners!"