Soto Windmaster Stove in Cold Weather?

The pressure regulators are really just a marketing gimmick. See:
https://backpackinglight.com/pressure_regulators_myth_part1/
for a review and analysis and some myth-destruction.

Cheers

I have both of those stoves.  I’ve used the Reactor in temps down to the mid-teens and find it works OK as long as I trick the fuel canister by placing it in a shallow water bath.  The lowest temp I’ve used the Windmaster in is 40 degrees; if it’s going to be colder than that, I would definitely go with the Reactor.  While I cannot completely answer your question, but it stands to reason that the Reactor’s integrated pot/burner arrangement and insulated pot cozy are going to make it the more efficient option for the cold temps you are asking about.  Plus it just feels darn good when the pot is removed and you can warm your hands up!