Lily's Dad, I've owned both the 318 and 322 now. I can say that there is very little difference in their capabilities and I suspect that the 322 with the gas Yanmar was likely quite a bit more expensive so I agree with the others that the 318 was the most popular due to cost and capability. It could do everything the 332 and 322 did at less cost, more of them were sold for that reason I'm sure.