I love how compact those old Canon primes are. I have a 35/2, 50/1.4, and 100/2. Those three lens plus my 5D2 and a 270EX flash would fit in the sort of small bag you'd use for a compact micro four thirds setup.
If I had the room in the pack and can stand sticking out with the weight/size, I would want a good zoom like the 24-105. That's because it's more weather resistant that those old primes and if I had to, I can leave that one lens on the camera.
I remember how caked with dust my DSLR got when I was backpacking in the Grand Canyon --- no way would I have been able to swap lens without getting my sensor coated in those conditions.
OTOH, my 5D2 with 24-105 is big and visible.
As for the 24-70 --- I own the f2/8L II. Sure it has one stop advantage and it has better corner sharpness than the 24-105, but, it doesn't have IS. If I had one lens on an around the world trip, I rather have the 24-105 or maybe the 24-70/4L IS.