Significant yes but both are aimed at the touring market. It's actually very common for these bikes to be compared by people thinking about a touring bike despite the differences.
And as with so many kinked comparisons, they only serve the purpose to justify a preformed opinion. Why are these people not comparing an F800GT witht he R1200RT and with the K1600GT? And... many, many people tour on a GS. What's up with that?
78 BMW R100S, 90 BMW K1; 99 BMW R1100RT, 12 K1600GT