I don't know enough about the Seneca, but I haven't heard any bad raps about them. I did walk through one on my dealers lot and saw a lot of fit and finish issues. It was a year + old so maybe that had something to do with it. My 35SK has had it's share of minor issues but nothing major. Has power to spare and averaged 9.6 mpg pulling my F-150 1,000 miles from NW Missouri to Hot Springs, Ar. and back. Comfortable ride with very little engine noise. There is no inside rattles or creeks going down the road. I'm very pleased with it so far. Hope this helps a little. Oops, if you plan to boondock quite a bit, you'll want to look at switching to 6 volt battery's with some solar help.
Rudy & Jenny
2014 Thor Four Winds 35SK, Super C
CRV, F-150 and Wrangler Toads