Depends on what you attack with next.

The blunt resist is +11% to all your direct damage and 10 higher base potency. The Twin buff is +10% to all your damage.

Basically using DK gains you 10 flat potency and then trades +1% direct damage + costs you 10% to DoTs until you recover the TW buff. If you use ToD or Demolish before you recover the Twin buff, then Twin is better. If you don't use those before you recover the Twin, then DK is better.