> On the other hand, if it's much colder than that, or if you regularly have to melt a
> LOT of snow then a white gas stove may be worth the extra weight.
If you have to deal with extreme cold you will have some trouble getting anything started. Even matches may be problematic if you aren't careful. However, the wise cold-weather walker takes precautions in advance.
I have seen pictures of Norwegians sitting the canister of a remote canister stove on top of the cooking pot while the stove was running - in severe cold. That sort of trick requires a long hose (!) and some real experience, but they seemed quite happy with the idea. I had better point out that there is a risk of melting the hose here, with a consequent BLEVE, so I strongly suggest you don't. I don't either.
However, much more to the point for serious cold weather with large pots: try switching to a propane cylinder. You will need to get gear compatible with the (usually Coleman) little propane bottles, but this stuff works down to -42 C (-44 F). You only need a little bit of warmth to get one of these going. Yes, they are heavier, but it you are pratting around at -40 C you need extreme reliability without fireball priming. Note that the Japanese do make adapters for these bottles.