It seems to me that you're looking at two quite different boats, space-wise. The Camano is, I believe, really about 28' with the integrated aft platform stretching it to 31'. Aft cockpit is pretty small. The Mainship 390 is I think really a 34 that they market with a 39'LOA including everything.
A big consideration to me, if I were looking to move to a newer boat from my MT 34, would be the walk-around flexibility of the Mainship. We are getting along, age-wise, and sending my wife forward to handle lines on the narrow walkway on a Camano is a non-starter. The bridge ladder access is also a lot more senior-friendly on the Mainship.