Well....the Terra is the newest rage in my stable, so naturally it is getting the most attention lately. It takes a bit to "sort it out" the way I like it to be....whatever bike. Though, I must say that with the Terra this process appears to be simpler and cheaper than all other bikes before. It's not really lacking much, to be honest. In contrast, it seems like I had to buy my Beemer twice to bring it up to my personal standards ($2,000 of new suspension, for example).
My F800 is definitely agile, mobile, & hostile. It's perfectly suited for long adventures that have lots of road time, and don't stray too far offroad into the nasty zone. Great heavy laden pack-mule losing no performance at speed due to anything being strapped on. Just fabulous on the open road, but a bit more than desired (in bulk & weight) in the mountain two-tracks, rocky creeks, & sugar sand I often encounter.
When I took a test ride on the Terra, I was shocked....never saw this coming. It looks big on paper spec sheet, looks a tad portly in person, and fairly close to F800 in side by side, but feels significantly smaller in motion. Hard to explain. You have to ride it to comprehend it.
So with the great road manners, I think the Terra will be grand for long distance riding, once I sort out the wind protection to my satisfaction. Otherwise, I missing or lacking nothing when transferring over to the Terra from my F800. The stock Beemer was no good here either, until I drank a 6-pack then pushed the BUY button for the $800 Deiserto 3 fairing. Wow that thing is fantastic and I would buy one immediately for my TR650 if it existed.
With the Terra, I can afford to experiment on mods since the bike was so much less expensive. You could buy two Terra's for LESS than the price of an F800GS, and hardly need to spend much more on aftermarket for a good time anywhere. I've been pleasantly surprised how well behaved it is offroad too. The steering is light, the bike holds its line, is well balanced with good traction control. Consequently, it has serious potential to knock the F8 from its throne. I may very well sell my F800 in the near future.
Generally speaking, my Pucker Factor will be comfortably lower offroad on the Terra than it was on the F800. There are places you really don't want to ride your F8. These spots will probably be no problem for me on the Terra. There is the difference you were seeking between the two (I think).
The TR650 is also a less complex bike....only one cylinder and fewer electronic whizmos onboard, than the F8. Love the 18/21 wheel sizes. The F800 is 17/21 and you still need a step stool to mount. I'm comfortable with tall bikes, but many people are not. I can't even remember when I last could put both feet flat on the ground. It's become addicting on the Terra....I like the feeling, though not sure why.
People complain about things, who have never ridden the bike. Like the suspension being only 7.5" of travel when everything else is taller. Longer is not better if it doesn't work well. The stock F8 suspension is horrible in front...long soft & mushy....so it's terribly hard to manage offroad. The Terra is shorter with a real cartridge fork that works quite well. A much better design for maintaining traction and control in rough conditions, with less rider effort....every time. Terra wins again, out of the box.
I could go on at length, but it doesn't matter. I really don't care what you choose to ride. Simply suggesting you test ride one and feel it out for yourself. I found the Terra owners to be very accurate with their descriptions of the sensations. I'm betting you do to.
HF