I don't know much about QEMU but it seems far more Linux-orientated. I also believe it mainly relies on KVM to provide near-native performance.
Bhyve is effectively KVM for FreeBSD. It's a very lightweight hypervisor, 100% designed on/for FreeBSD, making full use of hardware virtualisation features (VT-x,VT-d,etc) - In fact it won't work without VT-x.
Maybe VirtualBox is better than the credit I give it, but I tend to see it as more of a hobby/workstation hypervisor. Bhyve & KVM are more like ESXi/Hyper-V.
Thanks for the information. I usually have no need for virtualization, and run QEMU to debug kernels or to run an OS that needs hardware I don't have. BHyve sounds interesting, but I seem not to find any direct comparisons of these players on the internet. Perhaps I should set up all three, and check it for myself, as an academic exercise

Maybe there's a big difference between them, relative to running later versions of Windows. I see oblique references to that in the thread ...