Rippetoe.
A quote:
Modern corporate health clubs are designed exclusively for Exercising, Training being far less profitable. The standard industry model is 55 percent of the floor space devoted to "cardio" equipment, on which repetitive motions of various types can be performed while watching television. The remaining 45 percent of the floor space is dominated by exercise machines designed primarily for the convenience of the gym staff -- they are easy to use, easy to teach the use of, and easy to vacuum around.
Programs like P90X, CrossFit, or anything available on DVD that promises to keep your muscles "confused" are also Exercise. Any program that features random exposure to various types of physical stress cannot produce a specific physical adaptation, past a certain point that occurs relatively quickly. Their function is to burn calories, get your heart rate up, and make you sweaty and tired. They may do their job of providing Exercise quite well, and again, this may be all you need from a fitness program.
But certain people rapidly outgrow Exercise, and for them Training is the logical next step...