I went from a 2012 Road Glide Ultra to a 2015 Level III Wing. Here is my comparison:
Initially I found the Road Glide to have a more comfortable riding position, only because the seating position resembled the same Legs-forward position similar to your favorite chair or recliner. After 6 knee surgeries, this was important to me. You can achieve the same comfort by adding Mic-o-Pegs or highway pegs to your wing. I changed the handlebars on the Road Glide because I was getting shoulder and neck pain on long rides. I changed out the handlebars on the Wing to Helibars. The stock seat on the Road Glide (or any of my bikes for that matter to include the Wing) was good for about 150 miles before I would prefer walking. I always junked the stock seats and had a Russell Day-Long built. All comfort problems solved!
The stock suspension on the Road Glide was junk, especially the air rear shocks. I found the stock wing suspension to be slightly better and the rear shock more easily adjustable. I turned to Traxxion Dynamics for their "Mega Monty" upgrade and that meets all my suspension requirements. There are other options such as progressive, Race Tech, and a few more.
You may have tinkered with your Ultra's performance characteristics by changing cams, lifters, or bolt on engine displacement kits, exhaust, air breather, and ECM modifications to get more performance. Absolutely no need to do such things on the Wing. You will notice a big difference in performance right off the showroom floor. No shaking at idle or at anywhere in the power band for that matter.
Just do a search on this forum and you will see folks with 100K, 200K, 300K, 400K, 500K and higher mileage on their wings. How often have you seen that kind of mileage on a Harley without major top end overhauls? Just try and trade in a Harley with over 65,000 miles on the clock and see what you get. How many other motorcycle marquees sell replacement engines in their parts catalog? I'll take liquid cooled over air cooled for reliability any day of the year.
I certainly am not knocking Harley. Prior to this Wing, my last 5 motorcycles were Harley Ultra Classics, a Limited, and the Road Glide Ultra, and I rode all over North America on Harley's and they never left me stranded. It is just my personal opinion that the Wing is a solid touring mount, and with proper set-up, care and maintenance, should give your hundreds of thousands of miles and smiles.