don't get it mixed up.
Versamill 300 and 500 come with Sycotec
Arum or imill come with Jager.
the change in spindle is one reason Versamill stand out from other Arum vendors.
this is the spec sheet for the Jager spindle
View attachment 44532 you will find here in red that you obtain torque ever decreasing as rpm increases and power in/out increases; i.e. the more you spin it theres a point at which the power no longer delivers extra cutting power (40k rpm).
the sycotec spindle publishes their torque curve like this:
View attachment 44531 in red i have emphasized important information: you get the same torque at almost all speeds on this graph and peak power/torque cut off at 60k rpm
thats whats different between the two.
if this is too much info, Sycotec is better.