i used the T5 primarily b/c the O/D ratio is better than the others (inc supra) - mine is 0.78 - after all, the O/D is the only reason for such an upgrade) - (availability of upgrades - shifters and world class - and availability and cost of replacement boxes were close 2nd's). The supra box was readily available but expensive- I wanted a W58 (has the better O/D). The RX box made no sense to me, given the O/D.
The T5 box I scored for $220, (checked it out inside) used the dellow hydraulic set up - $1185 - bell housing, fork, release bearing, slave and carrier (Australian made was an incentive) - but already had a tail shaft. I used the standard XF clutch kit.
Now, if anything breaks I can grab another part easily....
still $600 for the m75 is very good....