When cutting the car off instantly, it drops the oil pressure immensily leaving it to coke on the turbo. This creates build up and as someone said earlier, blockage. This is not good. Make sure you give your turbo time to loose the oil pressure slowly. anyways, If I were you, I would pick a smaller turbo and go for low end torque. The smaller they are, the less time it takes to spool up and less lag. But, they are useless for top end. I would pick the smaller turbo because I never go to the track and race stop light to stop light. (Per say). Up to you though.
Also whats nice about smaller turbos means lesser psi needed and that means you dont need to build up your internals like you would if you had a large turbo. For example, pick a turbine like a T3. Not a junkyard/stock turbo, but an aftermarket one like HKS which is ball bearing (best kind) and is also aerodynamic, you will feel barely any lag and it will feel like you have just increased its horsepower. Very nice add on.
I once again highly suggest a smaller turbo for quick response street racing. If you are using the car as a daily driver more than a race car, then get a smaller turbo. You will feel no lag, and just gain power in the lower rpm bands. An HKSGT2835 will start building boost at 1500rpm to 2000rpm. These start working hard around 2500rpm to 3500rpm.
I feel this as an awesome setup for vtec motors because you have the boost in the beginning and the vtec in the top end. Perfect combo.
Hope that helped.