Both excellent Bikes. I have had a 650 for 7 years and over 100,000miles. My wife had a 700 for about 18months.
The 700 is significantly heavier and in a bad way - high up. The nice big under seat space on the 650 has been sacrificed for the pumps and stuff for the Fi and the ABS. The fuel tank is quite a bit smaller on the 700, although consumption is significantly better - steady cruising at 60-70mph (100-115kph) easily gives 70 mpg, umm about 25km per litre.
The riding position is somewhat similar although I would say the 700's footpegs felt a little bit higher and further back - just a cm or so but enough.
The 700's build quality was slightly poorer than the 650. The plastics look and feel cheap and flimsy. I am sure they are not, but it doesn't ooze quality. Not that the 650 oozes quality, but its better than the 700. Both bikes have a plastic sump guard but the 700's looks and feels like it would shatter if put to its intended use.
Finally, if it bothers you at all, I think the 700 looks a little "soft", again the 650 isn't exactly hard-core but it does have the look (and feel) of a bike you can use and abuse and it will come up smiling saying is that all you have got. The 700 would just whimper in the corner.
Have a look, and get registered, on XRV.org.uk for more advice than you could ever imagine about Transalps.
Whatever you get they are great bikes and you will enjoy, and either would be ideal for what you plan.