I've read a LOT about RTW bikes, and also have had some mid-size bike for touring SE Asia with recently, so perhaps this helps.

From everyone i've spoken to, and there's been some ardened riders, the most important points to consider when choosing the bike are;

1. Weight - can you lift it easily, or without breaking your back?
2. Simplicity - can you repair it, or do on-road repairs easily?
3. Fuel Capacity - larger tank the better
4. Availability of parts, and expenses thereof

After considering all of these, the bikes that were recommended were

1. Suzuki DR400
2. BMW f650/800GS
3. Yamaha XT660z Tenere

I've been riding a Kawasaki Versys for the past 6mths, and as much as it's an awesome bike, it's damn heavy to lift, and the engine is not so straight forward to repair. Having spoken with many RTW bikers, everyone raves about BMW's, but parts are pricey (however, some say they don't break down anyway, so don't need them). But, the resounding winner for me is the XT660z Tenere.

I met a guy who'd got his out of the box, added minor options such as handguards, chain oiling system and a sheepskin for his saddle, but other than that just got on a rode it - starting in Argentina and i met him in Penang, Malaysia. After all of that way, he'd had absolutely no problems at all, except a flat battery from a dodgy 12v adaptor fitted in Mongolia.

The XT is high, so will need long legs, but if you can manage it, it's got enough power, plenty of options to add, easy to fix, readily available parts, affordable price & can literally go anywhere.

I've checked out KTMs, BMWs (F800GS Adventure is close), but none of them offer all the things the Yamaha does. I'm not planning my next big trip and where to buy the Yamaha for it.

Hope this helps.

Keep on riding!