I've been through this. My son decided he wanted a bike at 16 instead of a car, and he was willing to pay for it. We started out with a Sporty. Got it during the buy back program. Did one long trip on it, he actually did 800 miles in a day, riding behind us. Found the bike to be VERY uncomfortable for distances, and stopping to accommodate a Sporty for gas was a real pain. Inside the first year, we used the buy back program to trade up to a Dyna. He liked this bike more, but the first trip we did on it, it vibrated so much we had to replace hardware that fell off on the trip. When we got home from that one, we traded him into a Road King (took a bath on this trade). That's what he rides now and he loves it. Mom was a bit concerned it'd be too big for him but he's done fine on it.
Hindsight being 20/20, I wish we'd just gone straight to the Road King from the beginning. Much better for touring, already has the bags and windshield he wanted. More stable than a Sporty and a lot more comfortable than the Dyna.