they're both the same weight, so i doubt there's much in it.
the 2009 Hemlock chainstays have a question mark of reliability hanging over them, after a few broke. a missing washer was thought to be to blame, but mine broke even though the accused washer was installed.
it's left me a little shaken actually; i'm a skinny coward, i shouldn't be able to brake anything. i certainly don't do anything like what oxnop is showing us in that Pace piccy up there ^.
(i'd want a run-up, and Downhill bike, and a landing transition)
the 2008 chainstays are fine, the 2010 chainstays are even stronger, and stiffer too.
they're both light bikes, not really built for abuse, i doubt you'll break either one in the peaks. I do like my Hemlock, but wish there was a hefty BFE Grrr! version…