If we're comparing binding dampening then the quality of the boot is absolutely relevant. Assuming a $400 dollar boot is going to have quality dampening, then you can hold all variables but the binding constant and make a comparative judgement.
But I suppose that gets in the way of a good ribbing.
With that said, I have Nike Kaijus ($350 retail for whoever gives a fuck), and I've never, ever had knee problems after riding, and I've been on Unions for the past 5 years or so.
Maybe Nivek is just a little girl?