I've yet to hear a bad thing about the S21's. I have a set of the S20 EVO's on another bike and I LOVE them. They are super sticky and the S21's are supposed to be more sticky and have 30-40% better life! That and the price would steer me to the S21's over the Pirelli's....
'13 Duke 690 "R", White
'13 Duke 690, 100% stock, Black - Sold
The S21 nor the Diablo Rosso III won't be available until next month.
I did some research and the Conti Attack SM also seem to be hand made in Germany and warm up quickly. They also don't need a "break in"...or so they claim.
The don't make a tire larger than 160/60. Interestingly the attack SM is only "H" rated - up to 210km/hr which is fine for me. In short the attack SM is for lighter bikes like ours (as wiwee stated). I was surprised my sizes were available so I ordered a set!