We've been using Big Block XL Lump Charcoal ever since we purchased our 18" Classic II KamadoJoe.  Some of the lumps are as big as two/three/four clenched fists, which burn for hours.  We easily do brisket cooks, starting the first at about 10pm, at 250 degrees, waking up to the kettle still holding the 250 degrees.  We really have no basis for comparison, since our KamadoJoe has only been stoked with the Big Block Carcoal.