dcampen- Yeah, some people call that LC finishing pad "black" and others call it "gray".
IME the black/gray pad is pretty soft, and it's lack of porosity makes it hard for product to soak in very deeply (which can be a good/bad thing).
Yeah, the diminishing abrasives get smaller/finer as they break down. The yellow pad is pretty coarse and porous compared to the orange one, but either one will allow product breakdown (as will the white). For serious correction I want the most aggressive combo I can get, and with the PC that means a yellow pad. It won't finish out as nicely as an orange one, but if you're following up with a white pad you should be OK.
The whole pad/product thing can get complicated (but fortunately that seldom matters in the real world

). Some pads are so aggressive that they will micromar paint, others aren't. Once you get past the pad itself being abrasive, how the product works with the pad's porosity can be a factor...sometimes a huge factor and other times not one at all.
I'd probably lean towards the yellow pad as I find the PC pretty mild even with 4" pads and I have a *lot* more experience with it than I do with the orange pad (but hey, that's just me). I don't really know enough about the Optimum line to give specific advice though
