They will both overclock your 2500K to its multiplier wall. They are equal in this category.
I had the same decision to make, and I chose the ASRock P67 Pro3 for my build. It has been great (overclocks my 2500K to 4.8GHz), and I'm just waiting for the fixed B3 version to arrive at my retailer so I can get the new one. I would recommend this board even to family and friends.
Does Dual Channel works normal ?