You didn't indicate whether you have ever ridden a Valkyrie before, so it's not clear if you are interested in comments about the differences between the beemer and the Valk. I've owned both, so I'll jump in.
I owned a 2004 K1200GT, which is the RS with more features. I swapped the higher GT bars for the lower stock RS bars, so my comparison with yours should be close.
As background, in the late 90's I fell in love with a BMW K1, which I nearly bought but passed due to impracticality, followed by a similar passion for the K1200RS sometime around 2000, but also passed for the same reasons. I replaced a Goldwing with a ST1100 at the time, but lusted after the Valks, both standard and Interstate.
About 18 months ago I fell into a great deal on the K1200GT, which was lightly used and in nearly perfect condition. Electric everything, fuel injection, ABS, Koni suspension all around ($2k!). Until I started riding it for a while.
Silly me, I didn't realize it's the same as the humongous K1200LT, which I previously rode and disliked. Both are tall, heavy, awkward; it's hard to find the kickstand and I nearly fell over numerous times trying to get it out. Climbing off and over the wide saddlebags was difficult.
The K12 has an electric windshield which is really noisy in every position. You have to buy huge ones to quiet the cockpit down, and they just look stupid. The shift mechanism is goofy and clunky. The power brakes are weird and the pedal can't be adjusted. The 'music' the engine makes is out of tune to my ears, and I didn't enjoy hearing it.
The saddlebags are flimsy, leak and are asymetrical. The seat adjustments didn't fit me in any position, and all became uncomfortable after an hour.
The bulletin boards are filled with all manner of fixes for every kind of problem you can imagine, which occur frequently. The rear clutch oil seal is probably the worst, costs $1-2K to fix, and they all will suffer from it after 50k miles.
I haven't disliked a bike as much as I did the K12, which surprised me cause I like the earlier ones so much. When I sold it, it became the only bike I've ever owned that I was glad to get rid of.
After going bikeless for a year, I gave in to my other wish, and bought a Valk Interstate, which share similar vintage and similar rarity with the K12. Bigger, heavier, better bodywork, more comfortable, infinitely more reliable. Perfect in almost every way. I really prefer a sport-tour crouch to the cruiser upright posture, but the Valk is still very comfortable. The factory seat could be improved, and I wish it had a sixth gear, but those are minor complaints.
It's a very different ride, but one that takes no time to get used to and enjoy. I don't even have to ride it to enjoy it - I just love looking at it and starting it.

Do I have any regrets about switching? Only that I should have done it earlier.
HTH, Gary