Steve & all,
correct. there was a comparison done in Zoom Magazine (issue ???) where they used the Trust T67 (oil-cooled, bush-bearing turbo) & Apexi RX6 (ball-bearing turbo) on the same car, where the Apexi was found to give almost 20rwkw more mid-range power but lacked in top end due to having a smaller exhaust housing.
power made with the T67 was about 304rwkw at 1.5Bar with a nice fat power curve, whereas the Apexi made about ~280rwkw with (as mentioned) better mid-range power.
Can't remember off the top of my head which issue it was. will check and reply here.
Also, fyi, i believe fullboost was seen at about 4500rpm with the T67.
cheers.