Backpackinglight.com did a write up. They found significantly increased performance in the Jetboil Sol in the low end of the stove's temperature operating range compared to other stoves. I can give you a link, but unfortunately you have to be a paid subscriber to see the article. In my opinion, a membership is worthwhile because of articles like this one.
What's going on? Well, the best I've been able to put together is that the aperture in the jet is larger than normal with a Jetboil Sol. It's certainly larger than the original Jetboil PCS's jet. Why didn't they just do that with the original JB PCS? Well, no problem in cold weather, but in hot weather, the gas pressure could get so high that you could get flame lift off where the velocity of the gas blows the flame away from the burner head and the flame goes out. Now, you've got non-combusting gas flowing over a hot stove. Not a good situation. How to prevent it? With the old PCS, you had a simple needle valve, and to prevent overloading the stove in hot weather, you reduce the size of the jet aperture. On the other hand, the Jetboil Sol has a regulator valve. The regulator acts to restrict the pressure when the weather is hot, thus you can have a larger aperture safely in hot weather. In cold weather, when the pressure is low, more gas can flow even at low pressure because of the larger aperture. Despite marketing spin to the contrary, it is not the regulator valve alone that allows for better cold weather performance, it is the regulator valve combined with a larger aperture.
Of course, any "tricks" you do in cold weather will also improve performance.
Regardless of what stove you used and what "tricks" you employ, be sure to use good gas. I've got a list of which brands are good for cold and which are not at
What's the Best Gas for Cold Weather?
HJ