I voted bricks. I use Kingsford Blue, Comp, RO, Wally world bricks... I have used a mix of bricks with Cowboy lump as the weather got colder (I live in the Northeastern Sierra, 5,000' Elv, 20-30*F, with a 10 to 15 MPH wind lately...). I think it helps get the temp up while the rig is warming up...