The problem is you're limited to 24 GB of VRAM unless you pay through the nose for datacenter GPUs, whereas you can get an M-series chip with 128 GB or 192 GB of unified memory.
Surely! The point is that they're not million times faster magic chips that makes NVIDIA bankrupt tomorrow. That's all. A laptop with up to 128GB "VRAM" is a great option, absolutely no doubt about that.