Welcome friend. Either bike will serve you well, because even if they are "only"500-600 dollar bikes, they are from established brands. Given the choice I would choose the Cannondale, for purely emotional reasons. About 10 years ago I rode a Cannondale and out of all the MTB’s I have owned (about 6), that is the one I would like to have back. Giants, on the other hand, when they first came out was discovered to have been made by Chinese prison labor (slave labor, as they received no money). Maybe Giant has changed their ways, maybe not, but either way Cannondales are a mythic brand. Every MTB’er should own at least one, once in their riding life. That’s my 2 cents worth of advice, take it or leave it but always remember that MTB’ing is all about the fun, not politics.
Thank you for the considering, I’m Chinese, and something i want to say is the most bike you can buy in your LBS may not made in china, but taiwan. the Giant KUNSHAN(in Shang Hai) bike factory seems only build low end bikes, and it’s mostly sold in mainland china, i have one, called ATX,not xtc, SO, don’t be guilty of buying a chinese bike. and by the way, the workers at mainland chinese bike factory may paid more than me, that’s true. because the most low-end level people is not the workers making high value exporting stuffs, it’s the vast of folk who support their life at a very low cost, so their labor can be so cheap.
just enjoy your bike!