Both are too heavy for their seat count as shrinks of larger models. The -600 is almost the weight (and same fuel consumption) as a -700 that most airlines are just opting to use the -700 and have more seats. Just 69 -600s ordered and delivered with no outstanding orders. The economics of the A318 may be slightly better but it's primarily flown by airlines already having A320s in their fleet and order the A318 to avoid having a second pool of pilots. Just 93 ordered and 56 delivered.