I've owned both as old models and still like every model of both ever made. I'd pick any RT over any Goldwing of the same value.
For me, Goldwinging is kinda dead and that bothers me. I belonged to a Goldwing club back in the heydays. Goldwings were very popular and high profile bikes. Rides, meetings, buzz, online and on-road. It was fun and I'd happily return to all that if it still existed. Now there are no clubs, no buzz, and I don't see Goldwings out in the wild nearly as much as in the past, or as much as I would expect. The new model didn't do much to revive the brand.
The world is sadly way past peak Goldwing as it is way past peak Sporttouring.
RT's are doing better than Goldwings. BMW won the Sporttouring wars by horrifying attrition and is the only Sporttouring Brand that is still alive by my observations. That counts for something with me. So, if you are ok with the expenses associated with that brand, and that the hugest of if's, then RT.
Best wishes with your decision.
(Disclaimer: For me, ADV bikes are not sporttouring. Excellent as they are they are something else to me, so I exclude those bikes.)