Difficult choice.
Lighter is always best for travel, but at the same time travel is such a rich and inspiring source of subject matter that you will be kicking yourself if you didn't bring your best gear with you.
It's interesting that nobody has recommended the middle-ground option of the Ti - intermediate weight, intermediate image quality and functionality? Most people either want full image quality or the most miniscule kit. Do you prefer the maximum freedom of travel experience itself, or is your mission to come back with the best shots you possibly can?
I would start your reasoning by thinking what you want to shoot, to what level of quality (how much time will you be spending doing photography?) then how much you want to carry.
So whilst I first wanted to say take the m4/3 system, I think the best option would be the 5DII+ three small prime lenses. The OM 21/2 is a peach. The Canon 50 is small and light, and gives you AF. For the tele I would look at a cheap old 135 with adaptor. Throw in a lightweight tripod with quick release for landscapes. Also a polarising filter and 72R filter if your sensor has some IR sensitivity you can use.
My city travel kit:
M9, 21/2.8 biogon, 50/1.5 sonnar, 135/3.5 canon ltm. Gorillapod + filters.
My landscape/hiking kit:
M9, 21/2.8 biogon, 40/2 rokkor, 90/2.8 elmarit-M. Gorillapod + filters.
In the city my normal lens is a fast and inconspicuous 50mm with excellent bokeh. Not super-sharp wide open, it's great from f/2 down. Super for people photos, indoor shots, and walking around once the sun goes down. I also prefer the old 135 in cities for architectural details and because it looks its age.
In the country, my normal lens is wider and less prone to flare. The tele is a little shorter but weighs much less, is far more resistant to flare and focusses closer for flower shots.
In either situation, my feeling is that three small primes should cover most things. Total weight should be about 1.3kg max, but the crucial thing is to make sure that camera+normal lens combination hanging from your neck most of the time weighs well under 1kg, and the weight of the other lenses can be distributed about your person. The smallest lens on the camera, and one in each pocket makes for a quick, light, and simple setup that will cover the vast majority of shots.
Good luck and enjoy a wonderful trip!