Pads that bind in the guide rails usually show much more wear on one pad (inner or outer) than the other. And, pads that bind just at the top or bottom will have uneven wear (top to bottom) from being jammed at an angle relative to the rotor.
In theory, the caliper can be removed, piston pushed out, and polished; but I have not had any luck doing this. If the corrosion is so bad that there is pitting of the surface, polishing won't save the caliper.
Piston corrosion is more of a problem in the "snow belt" states, where they use salt on the roads in winter. If you live in a warm dry climate, I would be surprised if that was your problem.
Pitted pistons are a lot harder to push back into the cylinder. But if you are using a big C-clamp, you might not notice the difference.
When a front brake is dragging on one side, the car will tend to drift to that side when driving straight ahead on a level surface at moderate speed (say 40mph) with your hands off the steering wheel.
When doing this test, be aware that many roads are crowned (higher in the center than on the sides) by design to shed water. The crown will cause the car to tend to drift toward the edge (usually right). Empty parking lots are a better choice.
