I bought the 18 first and love it.  I just bought the 22 cause I have a few big smokes.  Actually just did 8 butts for my daughters graduation.  I have noticed that the 22 wants more fuel at around 10 hours.  Only my second smoke on it so it is still working on Getting it fully seasoned.  I put the 18 on craigs list and when I got a bite I couldnt sell it as I want both!  The 18 will probably be my day to day smoker for the family butts but the 22 will do my ribs as I can lay them flat