410s are pretty low end kmc's, that might have had something to do with it. It actually makes little obvious/ a priori sense that a chain with thicker side plates would be noisier, that was a rhetirical question up there.
I really like the 510ZH's---on my setup they are always a bit noisy at first but quieten down quick. Currently I am rocking a 1/8" skinny 410---I didn't know you could get them as H's. Just checking to see how a $6 chain works, and it aint bad. It's pretty quiet anyway.