It shouldn't actually be a noticeable difference. HW virtualization means that unless the guest is doing I/O or needs to be interrupted to yield to the host, the guest is kind of just doing its thing. Spawning a new user space process in a VM should, in theory, be basically the same speed as spawning a new user space process on the bare metal. How that compares to the WSL1 approach of pico processes I don't know, but Linux generally has a very optimized path for spawning a process that I would imagine is competitive.