I don't really know and would also be interested in hearing.
Skied both the 2010 Grizzly today and the 2010 AC-50 up at Sugarbush and I thought the exact opposite of the common opinions on the 2008/2009 versions of these skis.
I normally ski old school P-50 Platinums for versatility and P30RC Orange Crushes for perfect groomers, both in 184. I'm 40, 5'7 and 190lbs.
Though I had lots of fun on both in 170cm length, the AC-50's seemed faster, more precise, and had slightly better edge hold on ice while the Grizzly seemed almost as rippy and significantly more flexible (particularly with the PS). No doubt that the AC-50 was better at ripping groomers, perhaps because it seemed much stiffer and beefier than the Grizzly (even in "power" mode), but when the surface is less than perfectly groomed the Grizzly's more progressive rebound felt more stable and thus the ski proved more flexible and forgiving for changing up the tun radius on short notice. I would take the Grizzly into light moguls and widely spaced trees, not so the AC-50. IMO the Grizzly was the better "All Conditions" ski. The reviews I'm reading of last year's models lean the opposite direction. Interestingly the Volkl reps pitched the AC-50 as the flagship for this year, whereas I heard the opposite from different reps last year.
Again, they were both great fun and I liked them both better than any other wideish "all-mountain" skis I've demoed including the also very fine Kaestle MX-88. If I didn't already enjoy the Orange Crush, I'd probably lean towards the AC-50 as my everyday ski since I mostly ski here in VT, but since I have no qualms using a pair of stiff old skinny GS skis on perfect groomers, I prefer the flexibility of the Grizzly's and will be adding a pair to the ski locker next month.