To explain why I am not in favor of Weider routines and yes in favor of Fullbody routines, I am going to focus on the principles of effectiveness and efficiency:

Efficiency would be simply to achieve all our objectives Efficiency would be to achieve our objectives using the best way possible resources and means at our disposal.

For example, at the time of obtaining a muscular development of quadriceps, femoral muscles, back etc, we would have 2 options:

Train everything separately. For example, quadriceps extension, femoral curl, pulley rowing etc. Simply make a dead weight.

would be effective get our goals through work isolated of all the muscles (first option), but it would be efficient make a deadlift as it has got the same effect in a while less and less wear.

Principle of supercompensación any stimulus applied to the body causes disturbance of the balance internal. 

The body fits according to the intensity of the stimulus, modifying metabolic processes useful to respond to the stimulus. during recovery period thereafter, the agency has a responsive increased. on the contrary, if recovery is not correct, there would be a supercompensación, and performance would decrease. 

Such recovery above the initial level is the point crucial and objective the principle of supercompensación during exercise decreases functional capacity of the subject, as it appears fatigue. 

Ceased physical exercise and therefore deceased phase of effort, activate internal mechanisms that will restore the ability of the subject above the initial level objective of the training can be treated as the maximum provision of the different skills that potentially (in theory) can achieve a person. genetics plays a decisive role in regards to the sports performance. the main objective of the training is getting a supercompensación, that is, put US above regarding the initial level and this is needed a correct recovery.

Disadvantages of routine Weider supercompensación the disadvantage I see the routine Weider is that does not allow a supercompensación, that is, damage accumulated in muscle fibers in each session is much larger than that the subject can admit. obviously, unable to generalize.

It is clear that a person who admits a high training volume, will work very well with a divided routine. But unfortunately, it is not frequent.

Beginners

The normal thing is to observe how the novices start in the gym directly with these routines, and from my point of view, the total volume of training (time under total weekly tension) is too high. An excessive load that will not produce supercompensation. In any case, if a fatigue. In general, what happens is that a novice person joins the gym and works Weider as bodybuilders do.

At first progress, but the progress is not eternal and be stall very fast. that's why i'm not in favor of it. 

Excess volume 

on the other hand, I don't see sense to be made exercises multiarticulares, very large and very heavy, and then make exercises that are focusing on the same area respect to the previous year.

My opinion is that it is not necessary, as simply add a workload that from my perspective spare, since the basic exercises is enough.

For example, if done Press banking 12 reps 4 series and are made funds in parallel 12 reps 4 series, do you really need to perform other 4 series crosses Pulley or other 4 series openings? for routines full body or full body environment hormonal I am in favor of the routine fullbody because the work with large groups joint produces an impact hormonal much more. 

On the other hand, damage with muscle fibers there but are to a lesser extent that the routine Weider, and therefore, recovery is faster allowing train more frequently a week, which will produce more muscle strength due to the expertise