I killed one and all it's cohorts today.
It isn't as tough as the giant bear because it doesn't have passive defense.
It's basically just a white normal bear and can be fought like one. It isn't really as tough looking as it...looks.
I also don't think it drops anything fancy...maybe gold and HP potions or something.
I hang out in that area a lot to kill bears for fomors and finest leather so I've fought the white one a few times.
Depleted Uranium is a war crime!