I looked at both bikes. I thought the Specialized was higher quality, although I just bent the crank last night and I'm not too happy about that. (On my Specialized Stumpjumper FSR XC)
Giants are cheaper because the frames are made en masse overseas. One of the big turnoffs for me about the NRS series is that the rear shock is a Rock Shox SID custom job. Say you want to upgrade to a Fox...good luck. I respect Giant in that they're frames are solid. I don't respect Giant in that they really aren't innovative at all and skimp wherever they can.
by the way, why are you only comparing Giant and Specialized? What about Gary Fisher, Cannondale, Trek, Kona, etc.?