I do not prefer either. They both work, and they both don't. What does that mean? Well, our body's are incredibly adaptable, and will become stagnant rather easily on one routine. Depending on how long you have been training, your body will adapt in 3-6 weeks on one routine. The point is to train one way for a few weeks and to swich BEFORE your body totally adapts. The only thing you should not do is OVERTRAIN.