In reply to Steve (The Steve): No replies Steve...
Perhaps others will reassure me but if it's really cold I mistrust gas stoves.
My climbing partner has a Jetboil that we mostly take when going up high but if it was likely to be cold I think I'd accept the extra weight and take the petrol stove (MSR).
For melting snow I would use a petrol stove, mainly because you need a big pan.
Someone might chip in with experience using those fancy gas stoves you hang up in your bivvi perched on a ledge above a 2,000m drop...not something I'm likely to be doing...