I think before folk describe the FJR as a "sports bike", they really need to ride a Yamaha R1 100 miles through the mountains in south western Arkansas (or any other twisties of your choice).
You will ache for a week, but the "grin" will make you want to do it again, and again, and ... well you get the drift.
Trying to compare the RT with either the ST1300 or the FJR is an exercise in futility because, in the end, the only comparison that really matters is a test ride. All three are excellent, all are different. As an LD rider I would be able to make any of them a very comfortable place to sit for the next 1500 miles but we each have our unique requirements.
Here is my ultimate test ....
If I were in New York and had to get to Los Angeles, and was told I had gas money and a small amount for the odd burger and cup of coffee, and those three bikes were lined up, which would I choose.
I would rule out the BMW because, comfortable and well-equipped as it is, I simply wouldn't be confident that it would get me there. Most times it would, but occasionally a UJ, or electrical gremlin will halt all progress. For reliability it comes down to the other two. Both are legendary in that respect. For sheer competence, neither can be faulted.
The ST is better equipped but it's a Honda, which means it can lack that indefinable feature we like to call "character", something the FJR has in abundance. It is, however, better equipped than the FJR (or at least the earlier variants were).
It's a tough call. My choice was determined simply by a bike being offered at a price I couldn't say no to. I've frequently found myself on bikes that were simply "there at the time". That certainly applied to the FJ1200A, although when I had a Honda VFR750, I hunted it down
The FJR/RT/ST debate is almost the definition of NEPRT,
It is Never-Ending because there isn't an answer, Pointless because the choice is unique to each of us, and Repeating because the debate is so much fun
Just like riding any of those bikes!