Read the compressor map!
At 7-8 PSI and a max of 3800 RPM, the T03 Super 60 is very nearly perfect. More boost and more RPM move you into a small-trimmed T04.
So if you're building a turbo 300 for towing/hauling or otherwisw acting like a truck, the T03 is the way to go. If you're looking to build a heavy, unaerodynamic, nose heavy hot rod than the T04 works better.