is this the first or second time you have asked this question? For answer like that, you either want someone to do your homework for you or you simply cannot be bothered to read a book. To answer this question would probably take you the combined learning of one or two years at university, so if you start now you might be done by 2010.

Well, you could technically do eihter. I prefer to fly I find it more comforting to know that I will not be spending more time in transit than at my destination. But should you have time and desire, the train is one excellent way of seeing the American landscape, and many consider it a destination in itself. You should look at what is along the way, and places you may want to stop off at and then decide if you would prefer to take the train or just fly out there.