The difference is the prices will come down as they not proprietry, whilst the MS ones wont. Of course on the 360 people figured out it was normal drives inside a casing so you could just swap out with normal drives still which is what I did on my 360.
PCIe4 drives for some reason have a horrid premium right now but it will die down as competition improves, for the vast majority of cases its random i/o thats king which is why a nvme drive is usually barely noticeable over a sata driver yet a ssd sata feels way faster than a hdd spindle. I expect practical load times on the Xbox with its PCIE3 specc'd drives wont be noticeably different to the PS5. It is a shame sony went the PCIE4 route.