I read a report on the WWW (dont recall where, but google) that said the Dakar was more of an 'allrounder' than the new twin 650. Yes the twin 650 has more power, but in the dirt, who cares - anyone who can use all 50HP of the single 650 is a legend.
Road/Two Up: twin 650 better
All Else: Dakar+Ohlins rear susp+TT front progressive springs > twin650
Single is proven VS Twin for longevity. In the middle of nowhere, I know what one I want.