I am about to order a 15" (non-retina) MBP. Rather than getting an upgraded hard drive and RAM from Apple, I plan to buy them myself and install them. For the hard drive, I am trying to choose between the Western Digital Scorpio Blue and Seagate Momentus. They both appear to have the same specs, same price (at least on (Amazon), and high ratings. Is it better to have a "bare drive" or not? Is there any other advantage that one has over the other? Also, Stevie L. on the Apple Store chat has told me that upgrading these myself will not void my warranty. Can anyone confirm for me that that is their experience? Thanks!