I really couldn't justify a newer Seneca, but I wanted one nonetheless. Did my homework, looked at a number of them, measured my driveway several times to be sure, and finally pulled the trigger on our 2006. The chassis isn't quite as refined as the Freightliner, and it's hard to beat the Cummins/Allison combination. But we love our Seneca on the Kodiak chassis, and I'm quite familiar with the Duramax/Allison power train.
As for the comparison with our Chevy Crew cab 4X4 pulling our trailer VS the Seneca, we went this way for several reasons. First and foremost, I apparently have a very large bladder, and our distance between stops is enormous compared to the truck and trailer combo. We enjoy getting there more than we used to, as it was just a necessary evil we had to put up with to be where we wanted to go. Now, the whole trip is awesome! And the travel is just another fun part of the adventure. Sure, it's more expensive. Had no payments on the truck and trailer. But we are much more comfortable. And I like Robby's comment above about feeling in command of the road. I can see what's going on up ahead much easier. The Duramax is plenty of engine for the 34SS plus our Jeep Wrangler toad, and we like the feeling of riding in a truck and on a truck chassis. My wife ruled out riding in a Class A right off the bat. She felt unsafe. Like a bb in a can if you ever get in an accident. I don't like being right up against the tow/haul limits of the chassis, and I get more headspace on the capacities with the Seneca. I really like this rig, even if it's not brand new. You would love the newer ones on the Freightliner chassis.
Oh, almost forgot, they are MUCH easier to work on than almost any Class A. Flip up the front end body work, and the whole engine is in front of you, accessories and all.
2006 Jayco Seneca 34SS
2006 Jeep Wrangler Unlimited Rubicon Toad