The Google maps in the market is an update to the factory installed version. If you download it, it adds new functions and settings and over all improves the original. It should also add Google Navigation, if you don't have it all ready, to your phone which is free to use as opposed to the VZ navigator ($9.99 per month).
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.