T34 as it will spool up quicker but the power will tail off over 6K as the T34 runs out of puff.

T4 lower torque due to longer spool up (i.e. lag) but will be having a holiday at the top all the way to 7.5K, laggy but may be safer for a 4wd drive car as the gearbox will have an easier time...! (Probably struggle to stop it exceeding 400bhp to be honest!)