vriceflyer is correct. The 406 is slightly longer. We picked up a little space in the aft cabin, salon and aft deck. The aft cabin layout is slightly different and I really like the walk around berth on the 405/406 as compared to the 370. The 406 has molded in steps which I really like. I also have an upper bunk in my forward cabin that I never saw on the 370. I know there are many other differences but those are the one that stick in my mind. But the biggest reason we moved up to the 406 is the newer technology. We sold an 89 Luhrs to go to an aftcabin and I wanted MPI engines, digital AC, etc, etc, The 370's seemed like they had the best of the old technology. The 406 had new technology.