look at the wings that clip around the cleat. If they are dented up and worn, that could be the issue. I ran into the same thing a while back where I had newer eggbeaters on one bike, older candys on another and there was a noticable difference between the 2. I tried replacing the cleats and adding shoe shields (sold by crank bros) because my shoes had some dents in the bottom from the pedals. Both steps helped a little but not a lot on the older set, but made my new pedals feel really nice. Finally I wound up sending the older pedals to crank bros and they put new wings on under warranty. They work like a charm now and all I paid was shipping.