general zfs/zvol question

Hello experts,

What would you think would run faster, all else being equal:

1. a freebsd vm, the image being file-backed (i.e. the empty vm image 
initially created with say "truncate -s 64g freebsdvm.img) on a freebsd 
zfs filesystem on the host, and the installed filesystem on the guest 
being UFS, or

2. a freebsd vm, the image being zfs-backed (ie a zvol) and the installed 
filesystem on the guest being UFS, or

3. the same as example 2, the guest filesystem being zfs?

for context this is recent stable/13, so OpenZFS, and the guest vm would 
have 4*vCPU and 16GB vRAM

I *think* example #2 would be fastest, if the underlying zfs vol was also 
using zstd compression. But I'm only guessing, and it's not a qualified
guess. I'm wondering if anyone has done this and what their impressions were.

thanks,
-- 
J.