Ultra M.2 is very similar to U.2. I think M.2 will be more prevalent in the future because it will have a lot, I mean a lot more SSDs than U.2, if you look now there are around 30-60 M.2 SSDs and around 5 are proper NVMe and also some 10-15 which can utilize the full 32GB/s x4 lane PCIe bandwidth. However only 1 ssd, Intle 750 ssd which uses the U.2 slot