Just for reference:
SnowPeak canisters contain a '15% Propane, 85% Iso Butane mixture'
Iso-butane boils around -12 C
-10 F is -23 C (that's well below the boiling point of isobutane)
Gas only comes out of the canister if the liquid is above boiling point
I suspect you were using new canisters? Because I think that the gas coming out of the canisters was almost entirely propane, at least at the start. What this means is that there may be not all that much propane left in those canisters, and using them in this sort of cold might result in no gas coming out by the time you have used about 1/3 of the canister.
Why the difference in performance time? It could be expected to be like this for any small upright stove, not just the SOTO. What happened is that when the stove started burning, heat was reflected back down to the canister and it started to warm the canister up, so the gas got warmer and continued to boil out of the canister. If you are *really* careful, you can do this in the snow, but it takes practice and skill.
Why was the Jetboil stove so much slower? Two reasons. The first is that the Jetboil stove is inherently slower, by design. Yes, by design. Jetboil asked Primus (who actually designed the stove) to make it 'underpowered'. The jet is rather smaller than on most.
The second reason really highlights the problem with the Jetboil design. The stove body blocks heat from being radiated back down onto the canister, so the canister does not get warmed up. Cold canister => low gas pressure => low gas flow => low heat.