I would guess that most carpenters working on-site don't use a mitre box
and instead opt for a chop saw.

I've got a power miter saw, and while I've never felt it particularly
unsafe, I just don't think it produces very accurate cuts. Factor in the
volume and the dust, and I'd much prefer a nice mitre box and saw. I've
only used junk - either plastic or wood. So I'm REALLY looking forward to
using a high-quality vintage one.

Thank you all for sharing your knowledge and advice!