Sorry I couldn't help you more, I gave it my best shot. So how about I share from personal experience....
I have owned 3 TT's under the Thor Industries brands, Dutchmen, Keystone, and Outback (in that order). Click on "My Profile" on the left and you'll see photos of all 3 campers I've had.
I've had good success with all three campers. They were not fifth-wheels, but the brand is still the brand.
The Dutchmen we had for about 3 years. It simply got too crowded and we hated the corner bed after a while, plus it had no oven.
The Springdale had no slides, and although longer, after a while, we really hated the floor plan. But it was a good trailer. We had it for 8 years and not a bit of trouble other than normal wear and tear. We did have a serious problem with it the first year we owned it. The tongue broke when towing. Yea, really. Unfortunately, it was just a fluke, luck of the draw, or a 3 leaf clover instead of 4. Whatever, we got the lemon. But here is where my loyalty to Thor Industries became solidified. They fixed the tongue, welded a new one on it when it was physically located 60 miles away from home and incapable of being towed. They sent two guys out and welded a new tongue on. It was far superior to the original. Like I said, it was a pure fluke this happened, but Keystone made it 100% right. All I had to do was paint the new tongue. This may sound like a horror story, but it actually made the camper stronger than ever and we never had another issue for years. The only other issue we had was a wire to the brakes rubbed and was causing a short. This happened in the 8th year we owned the camper, and I took it to an independent shop to fix it.
The Outback has been flawless. We've owned it for over a year now.I had a minor defect that warranty fixed (took 4 days from the time I dropped it off at the original dealer to the time I picked it up). I could have had it sooner, but waited till a Saturday to pick it up so I wouldn't miss work a second day.
I have seen hundreds of other Thor Industries brands, 5er's and TT's. Cougar is well made. Cougars 10-15 years old are still running around, no problem.
I know there are others that may have had issues with some of the Thor Industries brands. I think some of those issues are personal attitudes that get in the way too, really "turning off" the folks they need the help from too.
Denali falls right beside Dutchmen, they are manufactured at the same location, they use the same parts, appliances, everything. Watching how these campers are made, and I've been on a few manufacturing tours, they are all made the same way, by the same people, at the same plant, using the same materials. I would not hesitate to purchase a Denali if they had the floor plan we were looking for.
And as far as after purchase follow-up with your dealer, well .... than an entire different matter. All three of my dealers were as different as night and day, but all 3 turned out to be very good with follow-up after the sale. The first was Tom Raper in Richmond, Indiana (Dutchmen), the second was Stout's RV in Greenwood, Indiana, which is now Camping World (we purchased the camper at the same time "Stout's" sold out to Camping World. All our paper work said "Stout's RV" but 2 weeks after the sale they were Camping World. But (at that time), Camping World was marvelous with follow up as they inherited all the Stouts customers and contracts and such.
The third camper came from Wallnut Ridge near New Castle, Indiana. And by far, they have the Par Excellence in Service and follow up warranty work from anyone! They do 2 complete - after sale - inspections on your RV ... 3 months after you purchase it and 11 months after you purchase it. And if anything is defective, broken, anything, they fix it. They want their campers 1 year warranty expiring 100% perfect! They work very hard to make this happen.
The other dealer I have a close association with is Anderson, Indiana, Modern Trailer Sales. They are a Thor Industries (Primarily Keystone) dealer. But their service department is also Par Excellent! As I've had several dealing with them on small issues, like extra wiring, vent replacements, small upgrades, stuff, getting parts and accessories ... even getting me new wheels for my Barker Blue Tote! Very impressed with them too.
So, what I'm saying is, I think you can be comfortable with Denali, but definitely choose your dealer wisely. Ask lots of questions about the dealership itself, what to expect for follow-up, warranty work, customized work, ensuring your tow vehicle is up to 'snuff', not giving you a snow job and follow through on anything you might need them for. I think this is more important than the brand of camper these days. I think all the brands are made pretty good, if they are maintained, loved, and pampered a little by their owners!
Wow! I've really rambled. Sorry if I seized your thread, I just feel confident your looking at a right decant trailer and hope I can eliminate some of your concerns. Good luck!