For all my different cars, Redline MT90 has always been touted on the forums as the gold standard for manual gearboxes. So many real world stories of better shifting after switching to MT90. And I had good results.
But I can confidently claim from my real world experience in multiple cars that there is something even better than MT90, and I have switched all my cars to this oil as a result:
Ford XT-M5-QS Full Synthetic Manual Transmission Fluid
Just put it in the 4.2L, and the whirring noise I had with the transmission in neutral and the clutch out went away. Plus the shifting is just that little a bit better.
On my Lambo, the cold shifting was much improved with Ford XT, and I tried 6 different oils in that gearbox before determining the Ford oil was the best.