depends on the Make of your brake
Generally... stick to what the manufacturer uses.
Organic - are made from organic resins and fibers. They are good for recreational use as its bite is not that strong and they don't like rain or mud. Generate very little heat and that makes them desirable for some systems specially closed system hydros which don't hadle well thermal expansion of the fluid. Its life is rather short.
Semi-Metallic - offer very good braking power, low squeal, medium heat generation and medium lasting. A very good all-around pad. Some would say those are the best. As an example the Hayes pads are venerated as one of the best out there and they are semi-metallic. Made from a resin material with metal (copper, brass) chips inclusions.
Sintered - fully metallic, made out from low melting point metals powder (again, copper and brass alloys) by pressing them at high temperatures. These are the longer lasting, most powerful brake pads... the tradeout is that they squeal rather easily and generate a lot of heat which can be bad for some hydro systems. They cut thru the mud too.... but also some will wear pretty soon under wet (depends on the manufacturer).
For the Aztecs.... I dunno. Never used them but I've heard some horror stories in this forum about them. As someone would say... friends do not let friends to used Aztecs....
