It's hard to know exactly what's going on in that video, but it's not related to the amount or percentage of propane burned -- unless they used different fuel mixtures for the two different burners. Using different fuel mixes to try to make one's product look good would be pretty unethical.

Let's assume that the two tanks of gas have the same mix and amount of butane, isobutane, and propane and that the two valves are more or less equally open. Given these assumptions, there's a simple way to make the Soto Micro Regulator look good: Just use the right mixture of gases.

What do I mean? First, recall the vaporization points of the gasses used for backpacking stoves:


Now, how cold is that ice bath? Considering that liquid water is present, it cannot be colder than 32F/0C. In fact, unless crushed ice is used, an ice water bath is probably warmer by a few degrees, but for simplicity's sake, let's call it 32F/0C.

OK, for a needle valved stove to work, the fuel temperature needs to be about 10F/5C above the vaporization point of the mix of fuels. For a regulator valved stove, only a 5F/2.5C difference is needed. When you mix gas fuels, the vaporization point of the mixture is determined by the molar fraction of the various component fuels. Molar fraction is a fancy way of saying percent of the total as measured by by the number of molecules (not mass and not volume). All Soto needs to do is come up with a mix that vaporizes around 37F/2.5C and their regulator valved burner will burn reasonably well while a needle valved burner will struggle. Soto's burner will look like a wonder of science and technology while a standard burner will look like a dog.

The reality is though that the Soto burner, while it does have an advantage, only has an advantage over a fairly narrow temperature range. As I say on my blog the fuel mix you buy is far more critical to cold weather performance than the type of valve on your stove. You can also employ various means to keep the fuel warm. Keeping the fuel warm will give you a much bigger performance boost than using a regulator valve will. And, as I say on my blog post, if you're thinking about going out in really cold weather (below 20F/-7C), don't bring an upright canister stove; switch to a remote canister stove with a preheating mechanism so that you can invert the canister and run your stove in liquid feed mode.

I believe the Primus Express Spider you mentioned is just such a remote canister stove, one with a preheat mechanism. As such, the Spider should be able to operate (with the canister upside down) in weather down to about 0F/-18C provided that you purchase a fuel that contains only isobutane and propane and does not contain "regular" butane.

HJ