Hi, I just bought my first MBP last week. I have decided on buying a OWC external hard drive which is portable. Here are the two: OWC Mercury Elite-AL Pro mini 500GB with a Seagate HD Momentus 7200.4 or OWC Mercury Elite-AL Pro mini 750GB with a WD Scorpio® Black 7200rpm The size isn't the deal breaker. I am more interested in reliability and performance. Thanks a lot!