One probably has twice the calories of the other. Chances are its the same thing with serving sizes altered or something. Personally, I wouldn't take either. First off, these are Weider products which is one knock on them. Second - read the label - tons of sugar and not much worth at all. You might as well eat a bunch of cookies and call it a day (but don't). If you ask me, stay the heck away from any product that purports itself as a weight gainer.
-------------- "Don't follow leaders and watch your parking meters!" -- Bob Dylan
mega mass has too much calories it will only make you fatter and it would be difficult to define and have lean muscles. the price tells you the benefit.