I just got a Defiant punched up, and I already like what I see compared to my VG Nano. Even though I can get a ton of hand in it, my A game has always been throwing hard and playing straighter. The Defiant has no problems handling that.
Compared to the Nexus solid and the VG Nano, I think the Defiant is slightly less angular but gives a great midlane read and has more of a hard arc motion. Compared to my Nano, it is smoother and more predictable. I also like that it doesn't seem to burn up as often in the back. The Defiant also has a slightly stronger cover than the Nexus and right about the same or very slightly above the Nano.
The Nexus and Defiant are comparable. I think it comes down to the type of ball reaction you are looking for. More length/angle on the back- go with the Nexus. More midlane/hard arc- go with the Defiant.
My Arsenal (as of February 2012)Heavy Oil: Roto Grip Defiant: 3000 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