From what I have seen, the Critical Theory is the better choice. The core is designed to allow more flexibility with layouts, and that allows more versatility from strokers to crankers alike. My teammate has 1 of those and it is absolutely great on medium and the medium-heavy patterns we use at 1 of the houses around here. Once that ball comes out, more often that not, the string of X's starts. The MCP is a good ball but just didn't seem to be as versatile.
I recently started throwing a Defiant and that ball is a damn beast on heavy oil. Compared to my VG Nano, the Nano goes longer and is more angular. The Defiant has an earlier midlane read and is very continuous once it hits the backend. Carry between the two is better on the Defiant (I don't notice the energy loss that I would see with my Nano.)
Pair up a Defiant with the Critical Theory and you have 1 flat out awesome combo to hit the medium to heavy conditions.
My Arsenal (as of February 2012)Heavy Oil: Roto Grip Defiant: 2000 ABMedium-Heavy Oil: Track 919C: 3000 ABMedium-Heavy Oil: Ebonite Vital Energy: 4000 ABMedium Oil: Hammer Brick: 2000 polishedMedium-Light Oil: Track 505T: 4000 AB
