WinFsp allows you to create file systems. This project allows you to create disks that can be formatted with existing disk file systems (e.g. NTFS).

They both have their uses but in general I think WinFsp is more useful for most.

I am not familiar with ImDisk.

Sorry for the second reply, but I read a bit about ImDisk.

I think the main difference is that WinSpd is a general tool for creating disks as user mode processes, whereas ImDisk is a tool for mounting image files only.

It looks like WinSpd is a more generic tool. But I know very little about ImDisk so I may be mis-representing it.