Less stabilizer rattle, a PBT spacebar, rubber feet on the bottom to prevent sliding around . A slightly improved build quality (Hard to describe, it just feels a bit more solid). USB-C port. IMO Smoother out of the box as well.
Personally I think for the Heavy Grail, I’d want to go for the veracity steel finish if available. Polycarb in the future would be pretty unqiue as well!