On my 4th F8GS (keep selling them then realising my mistake and buying another
) and I've had a F650GS Twin as well.
Only ever had the pre- electric throttle versions, so cannot comment on that type except to say that I'm more than happy with a throttle cable, thank you very much
Fantastic, do-it-all machines IMHO that have very, very few foibles (un-like their horizontal pitoned relatives). Early machines had chocolate chains, slightly under cooled stators and head race bearings that you had to check and keep checking until you put your own ones in.
The 650 twin version felt smoother than any of my F8 bikes. Don't know why, but they have less power and are geared higher, so maybe those differences help it feel smoother. It might be that the 700 version released 2013 onwards feels similar, but I've not tried one. I adjusted the gearing on my F8GSs after having the 650 twin version by fitting the bigger front sprocket from the 650 version. Drops the revs by just under 500 in top but still pulls well in the lower gears when riding off road.
For me, the post 2012/13 bikes (700 & 800 version) have improvements that make them better than the 1st versions - no floppy front brake master cyclinder, re-positioned rear brake master cyclinder and the reg/rec was also moved to make it more crash safe. They also got a better center stand - proper legs and not those bent tube things the 1st versions came with.
If you want a pure road bike then the 650/700 versions are great. If you want more ground clearance or you have overly long legs, then the 800 versions would work. For me it's the ground clearance of the 800 for dirt work and (pathetically) I think they look reet cool (not that the 650/700 versions are hipahogapigs).
Go try the one that you feel will make you smile the most when you open the garage/shed door. If it does the same when you ride it, your onto a winner.
I've ridden bothe the latest 750/850 versions and thay did nowt for me, hence my 2014 F8GS still gets abused on the trails in the Dales when I'm down that way
All of the above is just my blethering opinions
SteveT
PS - And it only has switchable ABS, that doesn't really go wrong, unlike those later versions with electronic rear suspension and the newest 750/850 versions with all the fuel upstairs and more electronics than the space shuttle had (more to fail IMHO)