I test rode a Road King, a Street Glide, and a Fatboy S just because I could. I left with a 2017 Road King Special. Factory touring hot rod. That's me. Others on here have it right though, test ride, test ride, test ride, and you'll figure it out. I did.
You can't go wrong with either Motorcycle. And consider the Road Glide too. Like everyone has said, test ride each of them for a 2 - 3 hour ride. Find several road conditions too, freeway, city & find some twisty's to get a real feel of what is comfortable for you. These are bigger bikes than you are use too, so use your counter steering skills to control them. Also you stature will come in to play as well. Good luck and ride safe.
Love the extras with my street glide. The fairing does add a considerable amount of weight you have to get used to but after you do get used to it, you won't regret it. Love the cruise control and stereo and the better wind control Less fatigued with the fairing which allows me to ride longer and farther in more comfort.