I have both bikes. The 1200 adv is great cross country, two up,does well on dirt/gravel roads. I really like the ESA. It can do just about anything. Long mileage days comfortably, it can do more stuff off road than I would want to try with it....
The 800, in my opinion, is a great one up road bike that can do pretty well off road too. I can pull 600 mile days easy on it, (granted I did replace the seat)........ and it does pretty aggressive off road really well.....I would say a true 50/50 bike. I have ridden it fairly aggressive on the road with absolutely no complaints....same off road.
Mainly hwy use with 2 up, the 1200 is hard to beat...... about a 50/50 mix one up I prefer the 800.
11 Moto Guzzi Griso 8v SE, 12 R1200GSA, 2010 HD XR1200, 2012 BMW F800GS, 2008 Ducati Monster S2R 1000, 2008 KTM 530 XCRW
1977 Triumph T140 V Bonneville, 1976 BMW R75/6