The most efficient stove I've ever used was the Featherfire, which isn't pressurized but allows you to control the flame with a knob, snuff the flame and recover leftover fuel. But it lacks the simplicity of the basic pop can stove.

Stove build does determine efficiency, and heat output. I usually use the White Box.

Here's a rundown....
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki