Both have their pros and cons, and rider weight, riding style/type, weather and trail conditions are all factors that come into play when deciding which type is right for you.
In general, metallic pads (also called sintered pads) last longer and have more bite, and may perform better in wet conditions. They can also be a good choice for heavier riders or those who ride primarily downhill. Metallic pads can be noisier, and take longer to break in, but riders often notice there is less fade toward the end of longer descents.
Organic pads (also called resin or semi-metallic pads) run smoother and quieter, and have a greater range of modulation. Organic pads are made from a variety of materials, including rubber, Kevlar and carbon bonded together with resin. They are softer so they won't last as long as sintered pads, but they ride quieter and are easier to break in. These pads suit lighter riders and riding that doesn't require a lot of braking, such as XC riding, and are ideal in dry conditions. SRAM offers two types of organic pads, including one with its new Power compound, which according to SRAM offers more aggressive bite and increased power during sustained braking.
Chat with one of our techs if you have any questions about which brake pads are right for you, and do keep in mind that if you are switching from organic to metallic pads, it is a good idea to also switch out your rotors.