Tundra racing has a sale a couple times a year, e-mail them and see if a sale is in the works. If you want the biggest rotor that will fit a 18" wheel its their kit. The TRD kit will be a better long term investment, everyone says they are expensive to service but I have checked and its less than a hunderd dollars difference between replacing the TRD rings and the Stop tech rotors, you just have to shop around.
I my opinion its looks or function or price. The TRD kit will out perform the Stop tech kit but very few people will use the brakes hard enought and long enough to see the difference the two pice rotor design makes on the TRD kit.