If you’re going to use pcie lanes anyway then stick a m.2 at the end of it to benefit from mass scale of nvme drive production.
I also have a general distrust of sd cards and their write levelling. Maybe just rotten luck or fake ones but they never seem to last
> Sadly, having a microSD Express card slot on the Raspberry Pi 5 does not make a lot of sense at this point due to the cost of MicroSD Express card. An M.2 NVMe SSD is cheaper... For those reasons, [we] will not manufacture the HAT, but the design is released under a permissive MIT license, so anybody could manufacture it if needed. Maybe a microSD Express slot will make sense in a future Raspberry Pi 6, as prices come down.
The microcontroller on the hat is there to issue some SD-interface commands to light up the PCIe interface, and that's a combination sure to expose some interesting behaviors.