Me and one of my best friends have bought a new tenere and a F800GS last month and have been comparing last saturday.
We sticked to our conclusion based on personal needs:
The tenere is the better bike if planned long trips outside paved roads and eventually a RTW tour, the BMW is the better bike for daily use on tarmac and highway. Although the bmw can handle a RTW tour and the tenere can handle tarmac.
so @scottnet, your focus is on a RTW tour. If you have to choose between these two bikes, the choice is obvious.


more pics here: http://picasaweb.google.com/bonimacx/MotoVanJanEnBoni#

Few years ago i saw 2 bmw's 650GS with touratech tank in laos. 39 liters means a big range. More pics here: http://picasaweb.google.com/bonimacx...0GSSeenInLaos#
I don't think Touratech will be able to do the same for the F800GS.
The F800GS's front is just to wide. The hughe radiator for cooling the two cylinders makes it impossible.
Have a look at the F650GS front with touratech tanks and the F800GS without touratech tanks:



If BMW would create a F800GS Adventure version with hugh integrated tank, that would be the ultimate. A 1200GS adventure light version.

But finally, whatever you buy for a RTW tour, whatever "style" it is, will probably do fine. Take a look here: http://www.horizonsunlimited.com/tripplan/bike