I've noticed the same thing with my original Defiant. Great cover, has no problems with traction, but it seems to leave flat 10 pins or sometimes a flat 8-10. This is using multiple hand positions, playing up the boards to moving inside. Yet whenever I throw my Critical Theory or Rogue Cell, it's more continuous, hits harder, and carries better.
I'm guessing it's the core and potentially the numbers with it. It could also be the cover/core match wasn't as good as what we now see with the Hyper Cell. In my opinion, the Hyper Cell is definitely better in terms of carry and being more continuous in back.