Thanks,The reduced rolling resistance is helpful to improve EQ range as electric cars usually have worse range than fossil fuel cars.
The lower noise is also useful in an EV because there is less engine noise to drown out tyre noise.
The lower speed rating is a compromise possibly to achieve the above but it's OK for UK as speed limits are under 270km/h and the already low EV range would plummet dramatically at those speeds anyway.
So you have a choice of initially cheaper(?) non-MO or quieter, more efficient, more Mercedes MO. I would choose the MO myself for the quietness and improved range unless there is some other tyre label difference that would swing in favor of non-MO. Just make sure the MO is ok by Michellin for EV6.