i have both an 18 and a 22 the difference in fuel use comes down to how much meat you have i nthe unit. empty they run about the same on ehte same amount of fuel. since i dont use water or any other heatsink the only variable for me between my 18 and my 22 is the amount of meat in the cooker. my 22 and my 18 use the same amount of fuel cooking a 12lb brisket.
the BIG difference would be whether you use water claypots or sand for heat sinks. the 22 has a MUCH larger pan so more heatsink can be inserted in the unit and taht will make you use a LOT more fuel to cook the same amount of meat as a 18.
i use the 22 for just about everything and the 18 is pretty much rretired atm. it sits in my bbq shed until a need arises. the extra space is really sweet to have as i dont have to go through gymnastics to cook larger amounts and i have more choices as to where and how i want to arrange the food on the grates. more space means you dont have the edges of things hanging past the pan on the grates and singing the edges as much.
anyway good luck whichever you pick they are both excellent units.
the BIG difference would be whether you use water claypots or sand for heat sinks. the 22 has a MUCH larger pan so more heatsink can be inserted in the unit and taht will make you use a LOT more fuel to cook the same amount of meat as a 18.
i use the 22 for just about everything and the 18 is pretty much rretired atm. it sits in my bbq shed until a need arises. the extra space is really sweet to have as i dont have to go through gymnastics to cook larger amounts and i have more choices as to where and how i want to arrange the food on the grates. more space means you dont have the edges of things hanging past the pan on the grates and singing the edges as much.
anyway good luck whichever you pick they are both excellent units.