[NF] To upgrade or not (to Win10 from Win7)

As of today, I've got 1 machine (which I backup frequently for disaster recovery reasons). I should probably buy a 2nd machine, and I'm guessing that would have Win10 by default (fresh from the start; not an upgrade) and then I could have both Win7 and Win10 in which to test things, but perhaps I should just let Windows upgrade itself to Win10 since it's free?

Decisions, decisions....what would you do? I'm guessing "just buy the 2nd machine for a better long-term plan" (due to hardware life expectancy).

tia, --Mike