Actually, the S4 Snapdragon line is supposed to be the "less hotter" of the CPUs for smartphones out right now. There's a video where they did a "butter melting test". Yes, I said "less hotter" instead of "cooler" because coldness is technically not a measurement for temperature in science. Also, most people feel the warmness from their batteries of their phones more compared to the CPUs.
Here is the link of the video that I was referring to: