JWT uses ball bearing GT28's correct? They are smaller than Greddy's 18g's which can be both good an bad. The smaller the turbo, the quicker the spool, but obviously the smaller it is, the less efficient it will be in the upper rpms as well as higher boost levels.

I personally would prefer full boost at 2500 rpms with a larger turbo, rather than a smaller turbo that sees full boost by 2k, remember you can always downshift .