Carbon pads are the standard option, they're less harsh on the rotors, have a little better friction, and will last longer under dry, clean conditions. The sintered pads are designed for more harsh conditions, like if you ride in water, mud, and dusty conditions a lot. These conditions would normally eat up a carbon pad very rapidly because all that moisture and grit tears them up like sandpaper. The sintered pads will stand up to it better. The carbon pads will still work better in dry, cleaner conditions.
If you can find them, EBC Severe Duty pads are my choice when not on a budget. They cost a little more up front, but most likely it'll be the last set of pads you'll have to buy for it. I used to go through brake pads pretty quickly on my Warrior, even Sintered pads would only last me 3 or 4 days of riding, the Severe Duty pads appeared to be outlasting them ten-fold. The last time I had checked them I had about 5 day long rides on them and they had barely any noticeable wear. They might be a little more harsh on the rotors, but I didn't see any apparent difference in their performance over carbon and sintered pads.
