The STH-10 may be rated higher, but the 2/3T22 seems to pack more of a punch in my experience. I'm guessing it's due to the tone.
I am very familiar with the STH-10 as my former residence(Smyrna, GA) had a system of those sirens. Even though they were single tone the STH-10s had a nice sound. They had a great startup which caught one's attention and a LONG windddown time.
Agreed. 12-port sirens aren't my favorite, but STH-10s definitely sound much better than say, 2001s. The sound also seems to carry quite far for a 12-port as well.