I love my C18, very economical,reliable and powerfull. The best thing of all is you do not have the cycle count limitation associated with the C20. I heard of one guy had to have an overhaul at half life because he did a lot of short flights and ran out of starts. No problems finding spares either. Sure you have to watch the tot in the summer, but at least you won't overtorque the transmission. Go with the C18, I would recommend it.
