David, I like the look of the Guzzi, but it's only about 45 lbs. lighter than the RT. The F800GT seems a good fit, but emlevy pointed out engine problems were not remedied 'til 2013, which puts them in the same price range with a first gen RT1200 I've seen in researching French prices. Plus, the RT will nearly always come with hard bags and even a trunk, so I won't have to spend time and expense fitting the bike out.
Weight difference is greater than that. If a bike comes with luggage as standard then this must now be included in the declared weight of the bike.
Guzzi V85TT Travel (with bags) 243kg - without the bags it's homologated at 230kg. So 29kg or 64lbs less than the RT.
Our Blood Bike Group has two F800GTs they are 2018 models. To be honest we can't wait to get rid of them. For all year around use, we have had to buy, taller windscreens and hand guards, they do not offer the weather protection on the RTs. On top of that the servicing is more expensive, the 28k service is £1k for a full service and belt change. But my mate has a F800ST and he loves it. I have ridden it for around 4 hours and I wouldn't buy one, never ridden our F800GTs as I have always had the RTs.
I have to agree with Caspar, my blood bike group has several 800GT and they're the most uncomfortable bike I’ve ridden. I’m 6’2” and I find that I’m sitting in a cramped position, my wrists start to ache after a while. There's no weather protection. I wouldn't touch it with a barge pole, give me an RT anytime.