The MY2020 model M550 will have the new engine N63B44T3 along with the rest of V8s (750, x5 M50, x7 x6).
523 HP
553 lb torque
Plus i hope it will get new features and updates that 750 got (adaptive laser lights, alcantra headliner, remote start etc)
850 already has that engine. it has some good upgrades see PDF
Go drive the 850 adn decide for yourself. Video of it on the track
https://f92.bimmerpost.com/forums/sh....php?t=1578629