I recently bought a 3 inch precision cutoff saw.
http://www.coasteltools.com/prod_ct3.htm

When I first got the saw, I experimented by cutting small
(#4-#6) screws and bolts. The suppled AO disc cut them with ease.

I decided I wanted to play with more exotic discs so I
ordered Hertel Ceramic and Norton Norzon 3 inch diameter
1/32 inch thick cutoff discs.

Both the Hertel and Norton discs cut a piece of 0.90 by
1/2 inch wide sheet metal (cut on edge) with ease.

Now on to tougher stuff; a 3/16 chinese made toolbit.
Both the Norton and Hertel discs cut it in 10 seconds
without much toolbit heating or discoloring.
The generic AO disc caused significant heating and blueing
of the bit before it was even half way through.

At this point I'm pretty much ready to claim that Norton and Hertel
discs are equavelent, but what the heck, time for one more test.

I grabbed a 3/16 5% cobalt toolbit.
The hertel disc cut the toolbit in 8 seconds with ease and with
out much heating just like the other toolbit.
The norton disc has 2/3 the way through in 12 seconds and the
tiny slice I was cutting off was glowing red! Whoa says me.
Repeat the hertel test and it still cut the toolbit with ease.

So I pronounce the Hertel ceramic disc the winner at 2.25 each.

chuck