From what I've seen of the 3 roller mills, you can push them a little faster with less husk damage and less flour than 2 roller mills. The 2" roller gives a longer "valley" for the grain to fall into, allowing more contact time and again a smoother crush. The 3 roller mills also seem to separate more germ from the husk with smaller pieces, resulting in better efficiency.
I can't see any homebrewer grinding enough grain to justify the hardened rollers - now a homebrew shop yes. The more grain you grind, the less you would need the stainless option too, unless you kept your mill outdoors near a body of salt water.
I have a Crankandstein 2A and am very pleased with it.