I must own 11 Atlas bipods, IMO the psr was the worst. General consensus in the group I run with, the non rotating legs wasn't what is was cracked up to be. Buy spiked feet if it is sliding on you.
I like the Cal, it is slightly taller, but unless the bipod is under a full load, and the feet are dug in the ground, the bipod will follow the stock, the mount is pretty rigid.
Not bad mouthing a product, but that tightening knob on the bottom of the bipod has to me, always been a pain. Some are smooth and flat out work, the next a crap shoot, the Cal eliminates that.