Pretty much the difference between the two is a remote lockout,adjustable stem,and a step better groupo. Hard to tell if the brakes are any better or not,you'd have to ask over in the MTB forum. As far as lighter,I can't see there being even a 1 pound difference between the two. The frames are the same,the forks are the same(except for the lockout,BTW the remote lever and cable will add a touch of weight),the wheels are the same,the tires are the same. That just leaves the groupos,which aren't that far apart from each other in weight. I doubt you'd notice the dif in picking either bike up;you'd have to actually weigh them to see anything. And with only a step of so in difference between the groups,I doubt you'll notice anything in the shifting or reliability. So it basically comes down to the remote lockout and adjustable stem. Swapping stems isn't a big deal;many shops will do it for you as part of their fitting the bike to you. So you have to decide,is an adjustable stem,remote lockout,and touch nicer bits worth $800?