Bremco and Baer are two popular quality brands. No personal experience with them on 4x4s, but only on my vettes. The benefit to drilled or slotted is quicker heat dissapation. If you are off-roading, they may be more of a hazard. If you tow or haul and your vehicle is used for street only, then on a 4x4 they may be some help. Personally, I don't think they are worth the $300 for a pair. If you feel you need more braking power, then perhaps there is a problem with your brake system. If you are going for bling, they do look impressive when you can see the rotors through wheels!
Gnarls.