How P90X differs From P90X+ and how they compliment one another - taken from my P90X+X Hardgainers Thread
While P90X® is slightly superior to P90X+ in terms of it's ability to build muscle, P90X+ also includes a very important and essential element in determining actual muscle strength - ISOMETRICS.
Isometric strength is the most "accurate" in terms of defining your true muscular strength. While you may not be getting all "ripped" from lifting those heavier weights like P90X®, the isometric exercises Tony focuses on in the P90X+ will harden those bulging biceps into "nuggets of steel." Any of the movements where Tony has us "stop and hold," the hanging ab/core exercise, or 360 - chattarunga, combat push-ups, etc. are all isometric focused, and while P90X might make us ripped, the X+ turns us into "steel." And I'll take a steel-hardened (maybe less-defined) muscle any day over a bulging "ripped" muscle.
Isometrics will give your muscles "staying power" for the long haul. If you are an endurance athlete this is the kind of muscle development you want. Your muscles become like a coiled cobra, quick, springy, and full of force.
Yes, I can't wait to do my next round of P90X®, because I know the "hidden" gains I've received from the P90X+ will reveal themselves in definition as I gain from doing the next round of the X.
I do agree that if you're looking for "ripped" then P90X is the "gold-standard" but if you're looking for a "total body standard" of actual muscle strength then the additional component of P90X+ is the TITANIUM STANDARD (keeping with my steel metaphor).
Both the X and the X+ are integral in a total body fitness synergy. I am truly excited to see how these two workouts combined over the course of the next two years defines, strengthens my body back into a lean-mean fighting machine.
If you're looking at the results of size and definition as the components of success or standards for the P90X+ in comparison to the P90X® I do think you will wind up disappointed. But if you'll look at the process of the isometric conditioning as giving you TRUE muscular strength, then both P90X and P90X+ are the standard which all other exercise programs on the market will be measured against. And in my opinion there is nothing out there that even begins to touch these two without hiring your own private trainer - which we have in Tony (and a lot cheaper might I add).
The isometric function of the P90X+ routine is working in the "deeper layers" of our muscles, results that cannot necessarily be seen but they are there. For example, my transverse abdominus muscles (the deepest of the abs/core muscles) after the abs/core + workout, I can literally "feel" those muscles getting more developed and toned, like a flak jacket wrapping around my mid-section - I never had that feeling doing Ab Ripper X which seems to work my hip flexor/ab muscles more and my erector spinae (lower-back muscles). So abs/core+ is the perfect compliment to Ab Ripper X in my opinion.
And I know and I can feel that those high intensity lower-weight upper body exercises, while I may not get "Swarzeneggerized" with X+, these isometrics are strengthening me "deeply & internally" laying a foundation that when I go back to P90X® those superficial muscles that are the ones we equate to being "ripped" will start really bulging and getting defined, with tensiled steel strength! I'm into power not necessarily pretty. Then I will cycle back and forth between the X and X+ and soon 1-on-1 workouts, which I am really excited about.
We've got to have faith that Tony and the Beachbody Team know what he/they are doing. We've got to put out of our minds that the X is something more than the X+, or that X+ is something less than.
In the same measure I would encourage those who feel that the X+ is not giving them the same kind of intensity/results workout to increase your intensity. Increase your weights, go deeper in your Spiderman push-ups, bring your knees higher on knee raises, do 1 extra pull-up, kick higher & harder, etc. PUSH YOURSELF! Push yourself beyond what you think you can do - you did it with P90X®, now do it with P90X+! What this is saying is that your body has reached a certain level of fitness as a result of P90X and in order to take it to the next level you've got to work harder and more intense - BRING IT!
When you can stop comparing results you become freed from those results and 100% committed to the process of becoming truly totally fit and strong.