I currently own the v2 Serpent buggy but came from the OD (and before that the MP7.5). It has just over 1 gallon on it and the only thing I've broken is an inner rear wheel bearing. I spent almost enough money on "upgrades" to equal the price of the MP9, but honestly they were mostly tuning options that I would have purchased for the MP9 as well.
The main reason I chose the Serpent was that another local racer was going to switch from a Mugen (which he did). I knew that it required a fair amount of maintenance to keep in peak performance though I have not tried extending the interval to see if it's true. I did not choose the MP9 because no one else drives it locally, and to a lesser extent I was looking for something "different".
Pick what your heart desires and spend your hard-earned money how you see fit. Otherwise you are likely to regret your decision.