From the reports I have the new, made in Spain, XC's have much longer life compared to the old, made in Taiwan, S12's. One reasonably well known race team used only on set of S12 XC's for the entire A4DE, on hard rocky terrain, which is not the MO for the tyres. They were very happy and pleasantly suprised. The price is still up there though compered to some of the others. I Use Metzler MC5 intermediates most of the time, but have guys using MC4 soft terrain tyres in the wrong conditions who are rapt in both performance and life of the tyres. Mezlers on average are about $10-$15 cheaper than Michelin and on par with Bridgstone & Dunlop. I've used them all and they are all good. It's a bit like being a Honda, Suzuki, Yamaha man etc. You tend to stick with what you like and know.
Cheers,
K