If you are new to weight lifting, endurance based workouts such as MM will indeed build your strength. However, after a while you will plateau with this type of workout and will not be able to build more strength, just shape the muscles. An endurance workout features high reps with lighter weights. It is difficult to lift a heavier weight as quickly as Cathe sets the reps in her endurance workouts. A strength focussed series such as the new Gym Styles features fewer reps (in theory, although with Cathe this is not always the case!), a slower count, thereby allowing you to select a heavier weight. Of course you will build strength more easily with a slower count than with a fast count. The Gym Styles will then help you to bust the plateau you have reached with the endurance based workouts. Cathe's Slow & Heavy series, which features her slowest count of all, an 8 count per rep, is intended to do just that: bust plateaus and build optimum strength. And it works. I can lift much heavier wiehgts with S&H and with the GS series than I can with, say, PH or CTX upper.
So, if you are serious about building strength, invest in the GS series and/or S&H. There are no two ways about it!
Clare