Warners bats have as much moisture as possible taken out of them, to get the dead weight down .
I've yet to see a convincing argument for huge spines apart from the look of the bat
In theory, a large spine gives it an increase in stiffness from an engineering point of view, but I imagine the difference would be very small.
Edit: Actually, I just did some rough back-of-the-envelope calcs, and if you were to take off half of the spine on a bat like Warner's and spread the wood across the back evenly, it would make a significant difference to it's bending stiffness.