I prefer a canister stove for its speed an simplicity. Most calculations I've seen show you need to be out almost a week and using a pot with heat exchanger fins to end up being lighter than an alcohol stove. The real challenge is having a canister with just the right amount of fuel. That is much easier to do with alcohol.
In terms of low temperature performance, check out a Moulder Strip. People are using them to run canister stoves far below the iso-butane freezing point. Know what you are doing though... using a Moulder Strip on a hot day is probably pretty dangerous.