To be fair, longer term survival in -40 temperatures calls for a radically different strategy and a lot of specialized equipment. A multi-fuel/kerosene stove being just one case in point.

However, I'm not sure if that's what the OP had in mind. As a small portable (and/or emergency) stove I think either alcohol or esbit would work just fine for most people, unless they are actually planning to spend days on end exposed to -40 temperatures. But most people aren't going to do that on purpose, at least not without a good shelter in place.

I've read a lot about the supposed deficiencies of alcohol stoves in cold temperatures. Well yes, I'm pretty sure that trying to boil water on a small alcohol stove in the middle of some windswept icy plain wouldn't work that well. But no sensible person is going to do that anyway.

When it's that cold outside your top priority is going to be a decent shelter. All your boiling and cooking and whatnot will take place there, in a place at least somewhat protected from the elements. A good shelter will trap heat quite effectively so it will get warm fairly quickly, at any rate warm enough for an alcohol stove to work well. Keep in mind that the trangia stove is very popular with the Scandinavian military and outdoor enthusiasts in general, speaking for a very solid track record (even) in the Arctic climate.

I absolutely agree that a kerosene stove is a more effective solution in the extreme cold. But it can be finicky to operate, pretty darn dangerous in less experienced hands and requires a fair bit of maintenance to perform reliably. Unless you're going on a truly hardcore Arctic or mountain climbing adventure I don't think a kerosene stove is really necessary, or even ideal for most people.