There are quite a few types of carbon. What is everyone trying to do with it? That will determine what specs you are looking for. What is more important: chlorine removal or color removal? Is longer life more important than agressive adsorption? Is hardness grading important (for fluidized beds) or is particle size more critical?
Carbon is pretty basic stuff if used in the application it was engineered to meet. If you by vapor phase carbon for a water application it would seem defective, it is just not the correct application.