You will probably hear different things from everyone to whom this question is asked, and I too have heard many different responses. I will tell you what I have found in my experience.
Brake pad selection while using slotted rotors should be the same as if using standard rotors. There are no pads out there that "won't work" with slotted rotors. If you want race pads because they stop better and can handle a lot more heat, then get race pads, If you want crap pads because you just bought the slotted rotors so you look cool, then by crap pads. The scale of pad performance when using slotted rotors is very similar to the scale of performance when using standard rotors, the only difference is that the whole setup will be able to handle more heat up to the point where the friction material simply fails or the fluid boils in the caliper.
