Personal opinion, I don't think it is a fair question.
If you had said Meths against Gas, that would of been fair.
Gas, butane (Bluet) or propane / butane mix, stoves with preheat (coleman alpine) or without (coleman micro).
Personally I like gas for ease of use, but the only stoves that are viable all year round are ones that have some form of preheat system and run on propane / butane mix, which has better peformance in cold conditions than plain butane. I have seen gas cannisters explode/rupture in hot conditions so they have a down side there as well.
Trangia, bombproof, if a little large. Treated correctly one will last a lifetime and more, not the fastest, but dependable beyond belief, they are easy to light, I have used them in arrid, semi-arrid, tropical, temperate and arctic conditions, they have never failed me.
If you want one to burn cleaner use good quality meths with water in it. Smelly, I have never really cared when it has been making a brew in the harshest conditions, throwing a bit of warmth out into the bitter cold and giving off a faint glow that is very warming in it's own right.
Petrol stoves smelly, yes, dirty ( they can be if anything gets into the fuel), they can be complicated to get running and the time that you save on boiling water is lost on the amount of time setting it up and letting it cool down, you still require a pan set and still need to carry extra fuel. Fuel, they can be very thirsty beasties can petrol stoves and the amount of extra fuel that you need to carry can be considerable. You may need to preheat (in South Georgia we were getting through a quarter hexamine block to preheat a Peak1) and the availability of good quality fuel may not be gaurenteed.
Pros and Cons
Petrol stoves are quick once running and can be clean.
Gas stoves are quick clean and easy to use.
Trangia, everything included (pans and windshield), simple, easy to use, quick to setup, bombproof with virtually nothing that can go wrong with it, relatively cheap to run and realtively cheap overall cost.
Petrol stoves, may require preheat, can be complicated to set up and run, you may require to buy a pan set / windshield, if water gets into the fuel it is knackered, they are expensive to buy / run and cannot be thrown around as most are not robust enough.
Gas stoves, the fuel is reasonable price, but you still have waste at the end, the availabilty of fuel cannisters may be limited, you still require to buy a windsheild with most, you still require to buy a pan set with most, performance can vary greatly with fuel type / weather conditions and can be a little fragile.
Trangia, a little smelly, a little bulky and not that fast.
Sorry folks, but with the running costs of a Trangia, its general robustness and the availability of fuel IMHO I think it wins hands down
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