cookers are a real personal piece of kit, and in winter a truly vital piece of kit. everyone has their favourites. some people hate the trangia. i think its the weight the don't like. as for performance of the 25 and 27 model; i have used them both extensively in Ireland in winters, and had no problems. in proper arctic environments it may not fare so well though. has anyone experience of them in arctic conditions? i was weaned on trangias though, so i cant really give comparisons.
In real cold no meth stoves work very well. The whole principle behind the trangia-typ burner is that the alcohol gets vapourised. That is why you get a yellow flame the first couple of minutes when it's lit, and the blueish/invisible flame after a couple of minutes (that is, the vapourised fuel is dominating the combustion). As meths can go well below freezing, it is not only hard to ignite, it is also very energy consuming to get it to vapourise. Another factor here is the efficiency of the combustion wich is lower in colder temperatures. I've used trangias (both 'real' trangias, and the army kind) in cold weather (-42 was the coldest with a trangia, IIRC), and though I kept the burner in my pocket, along with the spare fuel it is no match for a good multifuel burner. It is possible to melt snow, keep it well insulated from the snow/cold ground and it will perform moderatly, but if you intend to do any extended winter camping, a multifuel saves you time and weight (in fuel) which will make you a hapier puppy. That said, I still think the civilian trangia, with a multifuel burner (several models fit into the trangia, e.g. whisperlite, optimus nova, trangias own etc.) is unbeatable in cold windy conditions. The flimsy foil-kind of windshields you get with most multifuelssystems are cr4p and makes the stove less effecient.
