Instead of stating more or less irrelevant reasons, I'd prefer to read something like "I am (have been?) one of the core maintainers and know Illumos and Bhyve, so even if there would be 'objectively' better choices, our familiarity with the OS and hypervisor trump that". A "I like $A, always use $A and have experience using $A" is almost always a better argument than "$A is better than $B because $BLA", because that…
In the long term if $A is actually better then $B, then it makes sense to start with $A even if you don't know $A. Because if you are trying to building a company that is hopefully making billions in revenue in the future, then long term matters a great deal.
Now the question is can you objectively figure out if $A or $B is better. And how much time does it take to figure out. Familiarity of the team is one consideration but not the most important one.
Trying to be objective about this, instead of just saying 'I know $A' seems quite like a smart thing to do. And writing it down also seems smart.
In a few years you can look back and actually say, was our analysis correct, if no what did we misjudge. And then you can learn from that.
If you just go with familiarity you are basically saying 'our failure was predetermined so we did nothing wrong', when you clearly did go wrong.