With a 1 liter, you can throw in 3rd and you don't have to change gears when zipping through the mtns. With a 600, you do a lot more work changing gears through the same curves. I've ridden for many years, and the extra low end torque of the 1 liters is just more relaxing to ride with.
It's not the top end hp, it's the low end delivery - with a 1 liter, you don't have to wring it out all of the time to move quick.
"Racing is life. Anything before or after is just waiting." - Steve McQueen