How it is on dirt depends on what you mean by dirt.
I have a 2010 F650GS which almost identical. It is very good on dirt roads...in my mind equal to the F800 as you do not need the extra ground clearance.
On two track jeep trails it is again equal to the F800 up to the point where you are going over stones, ruts, that need the extra clearance.
If you are going over desert or jeep trails, etc at high speeds where you are jumping the bike, the longer (and lightly better) front suspension gives you more travel when you land before bottoming.
the cast wheels are stronger but not as tough as spoke wheels. ie the spoke wheels bend/deflect energy, and the rims are steel (i think??) again so the bend before breaking. cast wheels are stiff...but break when high by high impact.
The cast wheels track better on spriited riding on pavement (ie don't flex) and are tubeless....which is much easier to fix on the road than pulling tire and patching a tube.
because the F700 is lower it handles the twisties better because of the lower center of gravity and flick between corner easier for the same reason.
Of course the F800 looks more macho.....except when you are tip toeing around the parking lot because your feet don't fully touch the ground.
Doing the alaskan dempster or dalton roads or the trans labrador on the F700 or similar long remote dirt roads is just fine.
If you are truely going off road...get the F800 or better yet a KTM or some lighter bike
hope this helps
ps the F650 gets noticably better gas milage.(regular gas) ...not sure about the F700
vtbob screwed with this post 02-02-2013 at 08:48 AM
Reason: added ps