cornering the KX500

I realize that I'm still new to the bike and the bike is new to me along with dialing in the suspension for my needs. But the first thing I noticed when riding my new KX500 is the rock solid cornering that I can only acheive while sitting down. I used to be able to out corner alot of 250 mx's in a turn on my KDX sitting or standing. I've ridden alot of 250's and had no problem cornering standing or sitting as well. I notice the 500 is kind of awkward while standing. I also realize the bike is heavier up front but I have seen guy's on 500's corner at blazing speeds while standing. what's the catch ????