If you believe the difference is only "
marginally better speed, performance, and handling", you haven't ridden a GT/GTL enough to know the difference. I had the pleasure of riding balls out with a friend on his 2018 GW for the 100 mile length of the Coronado Trail (Devil's Highway) :
The 123 miles of pavement between Springerville and Clifton make the perfect scenic roadway, experience Coronado Trail and The Devil's Highway is a must.
www.hannaganmeadow.com
It's one of the best tests of machine and rider I've had the pleasure of riding. The GW made a good appearance, but it's limitations became clear early. He was forced to do continuous scraping in tight corners to keep a spirited pace. Even there, I wasn't pushing my GTL to it's comfortable cornering limits. When we hit the one straight where you could open the throttle to the max, I blew by him when he hit 105 and I didn't look back. At that point I kept a pace more appropriate to the GTL, and took a rest break 50 miles later to let him catch up. BTW, this rider is no slouch. He was only limited by his GW's lesser capabilities.
You (or anyone) might argue that this is extreme riding that most riders will not do. And I would agree. But if this kind of riding is your thing (it's certainly mine), then the difference is everything. As far as the laundry list of K16 negatives you listed, remember that this is the Internet. Many who feel wronged are going to scream to the heavens to let you know about it. The forum is their megaphone. The problems you referenced do exist, but in far fewer numbers than the screaming would suggest. I needed an engine replacement, so I'm no homer. But my experience is that most problems are ironed out during warranty, and it's mostly trouble free riding from there.
Regardless, the GW is a fine touring bike, and if it's your thing, enjoy. Choice is good.