Pretty much my conclusion, too. It doesn't really matter within any reasonable time frame.
Generally for short trips (2-3 nights) I like alcohol. It IS lighter. For longer trips, >week, I bring WG. I just don't bother switching back to canisters for inbetween. I push the alcohol to 4-5 days at the slight weight penalty. Then go
directly to WG for 5-7 days with the weight weight penalty. I find this much simpler on my gear rather than maintaining a stable full of stoves to meet every possible condition. Indeed, I gave away several stoves and about 20 canisters since I dropped them to simplify.
Alky and canister stoves (unless you have the larger 16oz cans) are very similar in heat content. The raw fuel has roughly 5/8 the heat content of butane (isobutane, propane blends, etc.) The carrying mechanism is often a PET bottle for Alky, about a 1/2oz (worst case,) for up to 16oz. A 4oz gas canister has 4oz of fuel, and ~3.75oz of carry mechanism. (I think Jerry was saying 6oz for an 8oz canister... they are variable amungst the different manufacturors.)Adding the fuel weight and the can weight will quickly give similar results for either fuel. In either case, it is what we strap in our packs that counts, not *just* heat content.
That said, there are differences. High heat output is not really possible using alky. Canisters pump the BTU's out. Simmering and cooking is not really that great with alky. Turning down a canister to the lowest setting helps with fuel efficiency (less heat wasted.) Extra heat screens with alcohol stoves, more fiddle factor. Excelent "green" efficiency with alky. A lot of less tangible things that can still mean you want to use a canister stove or push an alky stove beyond pure weight efficiency. The "packet" nature of canisters can be bad, as Franco said. Or it can be good. How do you handle a partial canister? But, these are all subjective. Really hard to call it based on these items.
My thoughts only . . .