Dynamic xDrive is even more dynamic driving / performance driving capable - especially traction & stability in high speed cornering are improved. It will provide even better handling & steering. There will be also off-road advantages.

Pair Dynamic xDrive with Adaptive Drive / Dynamic Drive system -> perfect combination.

SH-AWD is heavier and not so much connected to other car systems like Dynamic xDrive will be - also thanks to FlexRay. So Dynamic xDrive is expected to be more efficient than SH-AWD. The idea behind both systems is identical, but realisation is different.

Btw, mind that BMW are quite new to AWD systems - they are enhaching the system with time. New testing facilities, and better colaboration with outsource engineers are providing much quicker & more efficient development.