My 2 cents ...... Love both bikes, but the older you get one must start putting age into the factor when deciding on which model. At 70 years old I went with the 2017 Ultra Limited Low. Easier slow speed handling, gauges and infotainment closer, easier to read and it still handles beautifully and comfortably all day long at 75 mph on Interstates. If your eyesight is to the point where you need readers that further distance on the RGs gauges can be a problem.
My first Harley was a RG custom so I have a deep rooted love for the shark nose. That being said, I think the highway handling characteristics gap got smaller with the rushmore models. In my opinion, the RG fairing is the best there is on the slab. I haven't ridden anything else I'd call better including BMW's and gold wings. But, the 14 and newer batwing is so much more improved over its predecessor that it's a much closer second in my opinion. I just traded my 17 Road King in on a limited. I didn't even consider the road glide this time because IMO the bars are absolutely horrible. I couldn't own the bike for 2 minutes without replacing those handlebars. Also, and this may be a misprint on Harley's website but I believe the RG has less suspension travel. Ground clearance is almost an inch less than the limited.