You can't get a 128GB M3 Ultra, it's also more expensive. For some workloads the Studio is better, for others the GB10.

It is unified memory on this one

I took ~ to be a "singing tone" for some reason till I saw sibling and realized it might be an attempted strikethrough xD

That won't hold much benefit as SOCAMM2 and LPCAMM2 get more popular.

It's actually reversed. The GB10 chipset has a TDP of 140w, whereas M2/M3 Ultra pulls over 250w from the wall: https://support.apple.com/en-us/102027

AFAIK, for the unified bandwidth, it depends mostly on the CPU, for M4 Max (I think it's the default today?) it does ~550 GB/s, while GB10 does ~270 GB/s, so about a 2x difference between the two. For comparison, RTX Pro 6000 does 1.8 TB/s, pretty much the same as what a 5090 does, which is probably the fastest/best GPUs a prosumer reasonable could get.