The difference is that Musk can do twice as much for 1/10 what Nasa thinks the program will cost, which is never what the program will actually cost, and Musk will do it in half that time to boot.
The guy is an unhinged manchild, but if what you care about is having your money well spend and getting to Mars as cheaply as possible, he's exactly who you're looking for.
I do find impressive that SpaceX engineers figured out reusable rockets and now we can send things more cheaply out to orbit. But in all seriousness, should we care about getting to Mars cheaply? Or do people care because Musk came along to convince them (and the US government) to invest in this venture of his?