In reading other posts on Mud about this, my understanding now is that the VC operates as a limited slip device and transfers power to the non-slipping axle. Locking the CDL accomplishes the same thing, but requires driver input and is not advisable on paved roads. Several people have posted that the VC is particularly useful on icy or slippery paved surfaces, as it helps maintain traction but does not bind the drivetrain as a locked center diff does.
I don't always drive with the CDL locked (I do have a CDL button installed and have done the Pin 7 mod). According to other posts here on Mud that can lead to overheating the VC, so I'll probably start locking the CDL more routinely off-road. I like to have the CDL unlocked in tight turns, as it binds the drivetrain.
So, to sum up, I'm keeping my VC as it works fine. And I'm going to lock my center diff with the CDL button when I'm driving off-road in the future.
I think Toyota got this one right, and I'm sticking with the original design.