It's all the same in undergrad. The difference between these schools is their graduate programs. They are not working any harder or easier than a student at Oregon or Washington. Admission standards have nothing to do with the difficulty of the academics.
Not true. I spent two years of undergrad at Oregon and two at Washington. Very different academic experiences. Oregon curriculum wasn't much more challenging than the curriculum at my high school. And like someone posted above, when you're in classes with brighter peers, the expectations are higher, the curve is set higher, and the faculty have to be on their toes. UW had higher quality faculty even at the undergrad level.
Of course if you're a competitive runner there are other issues to consider...