No" data" here. All I know my Memphis Pro (double walled and larger ) vs my Traeger Lil Tex, heats up and recovers faster, as well as using fewer pellets.
The Pro will get much hotter than the Lil Tex... Any pellet pit will consume more pellets at higher temp settings and/or operating in colder weather.
I couldn't tolerate using the Traeger in the cold so it was Winter stored.. The diffrances between the two is more than a double wall.
I do believe a double walled pit is more efficient - any pit. ..Is the cost worth it? That is a personal choice.
The 800 series isn' t a true 100% double wall... For a more scientific approach to a double wall pit, look at Cookkshack's comparison between the PG 500 and the PG1000. Pellet consumption is listed.