12:15 a.m. on February 3, 2009 (EST)
Funny you should ask this question today. I was searching through boxes in the storage facility for some items for a course I am teaching this weekend and came across a post that Jim S made in the course of some experiments that he and I were making on efficiency of cooking on backpacking stoves. Jim, being an engineer who loves to experiment like a scientist, did a whole lot of experiments, while I, as a scientist who likes to think up the theoretical explanations, tried to explain away his results. The article was posted on rec.backcountry.useful when it was part of Views From The Top. It may still be in Dave and Alicia's archives.
To briefly summarize:
The most efficient heat transfer is with an anodized aluminum pot (like the GSI pots and their later imitators from MSR and others), combined with a heat exhanger (like MSR's) and proper windshield. (Be very careful with windshields with stoves that sit atop the fuel container, like the compressed gas stoves that screw on top of the canister or the Svea 123 - you can reflect enough heat back on the fuel tank to explode the fuel!). The pots with the attached heat exchanger (JetBoil, Primus EtaPower, MSR's system) are a recognition of this efficiency booster. These pots are anodized a dark color that transfers infrared (that's the heat part of the spectrum) very well. Plus most of them have engraved grooves on the outside bottom that serve a heat exchanger function. Aluminum spreads the heat well and evenly (as well as cast iron, but much faster), so burning and scorching things is minimized.
Titanium pots, while much lighter than anything else, are poor heat conductors (that's why the SR71 was made of titanium - dissipate the heat generated at hypersonic speeds). But Ti pots are so thin that the heat will pass through pretty readily. BUT this means that there is a little circular hot spot that matches your stove's burner. Not a problem when boiling water, but it will scorch snow when you try to melt it without first putting enough water to a half-inch depth in the pot (been there, done that, and everything tasted like scorched snow for the rest of the 3 week climbing trip - most godawful taste you can imagine!). You can readily burn soups, pasta, and other things if you aren't pretty careful. The heat exchanger and windshield are important here as well. Ti pots are also dark to pass the heat well, even though they are very poor at a uniform distribution of the heat.
Stainless is popular because it is easy to clean. But you want to blacken it to absorb the heat better. Jim S experimented with painting pots with black header paint. This worked very well. However, he cured the paint in his kitchen oven, which created fumes that required opening all doors and windows, plus getting a fan out. His wife did not appreciate this use of her oven, as I recall. Again, the heat exchanger and windshield boost efficiency quite a bit (about 20%, according to his writeup). But it still fell short of the anodized aluminum and titanium pots.
Non-anodized aluminum works well, though again, better when blackened.
Over the years, I have accumulated all sorts of pots and cooking kits. One thing that Jim noted in his experiments is that cooking systems, such as the Sigg cooker for the Svea 123 and the Bibler and Markill hanging stoves (and Jim's numerous homebrew imitations of the Bibler and Markill) work very well by having a windshield/flame director arrangement that keeps the flame directed very close to the pot's sides. The MSR SuperFly hanging kit is a similar arrangement. I have found that the SuperFly with the GSI pots boils water in incredibly short times - fast enough for a liter that I better have the rest of the meal ready to go before I light the SuperFly (down around 2 minutes or less). These days, I use only the GSI pots, sometimes with the MSR heat exchanger, with the SuperFly, Primus MFS, MSR XGK, and MSR SimmerLite, always with the appropriate windshield, and always with the pot lid until reaching boiling. This goes for the casual weekend backpack and for the extended expedition and everything in between. The stainless and titanium cook kits haven't been used in at least 10 years.