It's commonly thought that there are two methods of training: structural training and functional training. And once one's training becomes too much of one, then there is benefit and progress to be made by implementing the other.
Structural training is training that affects one's frame and build - structure. Functional training has to do with performance.
For example, a bodybuilder whose leg development has diminished or plateaued will surely benefit from more functional training for awhile. So, if said bodybuilder were to increase his 1-rep max in the Squat from 500 to 700lbs, then it's reasonable to assume that his leg size would increase as a result.
There is no absolute best way to train, but rather to vacillate between functional and structural training or to combine both types in single cycles.
Personally, I believe the Westside Barbell methods of training are superior to others as they incorporate the Maximal Effort method, the Dynamic Effort method, Repetition Failure method, restoration training, plyometrics and general and specific conditioning training. This eliminates the need to constantly find a new set&rep scheme to avoid accommodation. It's actually a rather complicated system to employ correctly and to its fullest potential, but when done, I believe it offers the best way to achieve specific, continuous gains in size and strength.