One thing not mentioned is ease of servicing: I really hate having to remove upholstery to do inspections, it's a real hassle trying to get those self-tapping back in without having to go up a size. The other thing is access to the back of the instrument panel - Robin aircraft with removal panel is the way to go. Another thing is the engine cowls some like Cessna and Piper have those Dzus type fasteners which eventually fall out and the holes enlarge.