Sounds to me as if the pistons are moving unevenly. This can normally be sorted by pushing the piston out to its limit (do not pop it out of the caliper, it's a big hassle to get back in and bleed the brakes then) and giving it a good clean. Then lube then edges of the piston (I use the brake fluid that is in the hose) and push it back in. Needless to say, don't do this with the pads installed, as you will contaminate them. Align the disc caliper with the disc rotor and away you go.
As for the front brake having less stopping power, this definitely shouldn't be and there are a few possibilities;
1. Worse quality brake pads
2. Brake needs bleeding (air in hose)
3. Contaminated pads/rotor
I'm sure there are other possible reasons, that's just all I can think of now.
Finally, the durability of brake pads will be affected by the compound that they are made from, the conditions you ride in, and "burning them in" pre-ride. The only real solution is to not brake ; )