Sorry, this is probably not what you are looking for, but I do hope it will help.
You will also find it reasonable that unless someone took both Veritas
and MGMAT, you wont find too many good responses. The more reasonable thing to do maybe is to attend 2 class sessions of both Test Prep companies and see what works best for you. The companies will let you do that if you ask nicely. Coaching should help you with fundamentals. If they focus TOO much on tricks and tips, I dont think thats the right place if you are interested in a 700 or more. Even if you take classroom or online coaching, the bulk of the work has to come from you.
The due diligence part is important, but its more important to truly understand how a test prep company should help you. Otherwise, you will find yourself unsatisfied.
While you are looking at MGMAT and Veritas
, you may want to consider GMAX Online also. Just an option.
I am again sorry if this is not what you are looking for.