My wife has a 98 Ford Explorer and the drivers wheel is loaded with brake dust; bad caliper?

My wife has a 98 Ford Explorer and the drivers wheel is loaded with brake dust, and the penger wheel has very little. I really don't feel any pulling when braking or when driving. I also notice the driver rotor seems to be wearing a bit faster and the psnger side looks like normal wear. So, which calipre is bad, the driver side or penger. I am thinking the driver side might be sticking just a little bit. I have cleaned all the slides and put brake grease, but still the same results.