Hi Konrad, welcome. Please tell us a bit more about yourself: where you live, are you young or old? Knowing this helps us give better answers.
I have a 2003 R1150RT I've been riding since last November and I love it. I'm in northeast Ohio where the weather is cool to cold from October through April, and my RT lets me ride pretty much comfortably during any of those months (as long as there's no snow or ice on the road). And the handling is superb; not quite sport bike good, but very close.
From what I've heard the R1200RT is a little bit better than the R1150RT in terms of power and ride comfort.
Also, there are different generations of R1200 bikes ranging from 2005 through 2018. Earlier ones are air and oil cooled, later ones (after 2010 I think) are water cooled. Each kind has its advantages and disadvantages. Oil cooled are easier to work on but have shorter recommended service intervals. Water cooled are harder (and therefore more expensive) to work on, but have longer service intervals. An example: valve adjustment. On an oil cooled engine it's very easy to do but needs to be done every 12000 miles. On a water cooled engine it's a much bigger job but it's needed only every 36000 miles. I'm not sure the exact numbers, but this is the basic idea.