+1

If it's a road trip where you don't need to worry about the odd bit of mud take the BM. If it's an off road trip where you need to get from one bit of mud to the next take the KLR. Both will do the miles, it's just how fast and how hard you want to work.

South America seems to have everything from deserts to six lane highways, it's your mix that IMHO should set the choice. I took to a big GS on sand and mud quite easily, but an F650 or XT600 are noticably lighter and once you've tried both I think you'll see how a 600 is the logical compromise between a true trail/mx bike and a true tourer for a lot of people. I think you need to find some rough stuff and ride both bikes on it if thats what you'll be doing on your trip.

BTW, are you mechanically familiar with both bikes in equal proportion? Starting from scratch I'd be happier with KLR technology, but there are plenty who know their BM's. It's you and your bike that counts, not brand image or past performance, but you'll know if your GS and it's hydraulic cylinders are a one off or not by now I guess. How many miles since the last failure? Did you find a cause and remove it?

What's your insurance, import/export plans? The KLR is obviously worth less, so should leave more in the budget after it's actually sat on it's own wheels and ready to ride, but I wouldn't worry enough to switch bikes if you are planning Sierra del Fuego to Mexico City in a fortnight. Likewise the KLR will be cheaper to replace if you trash it.

My own choice is of course much harder. An MZ that makes nice blue smoke and can be left in any city in the world with the keys in the ignition, or the Triumph-Ural that doesn't fall over when I forget to put my feet down

Andy