The Blue is their normal range model and is 7200 RPM. The Green is between 5400 and 7200, probably closer to the 5400 mark. Their Black version runs at 7200 RPM but is faster than both. The green version was designed to be a low power alternative and performs accordingly. I am unsure about the seagate. I would, however, recommend the WD Caviar Black 500GB SATA. Some may recommend samsung spinpoints, saying they are faster and more reliable. The recommendations appear consistent. The only reason I do not is because I have no experience with them (They seem scarce in Canadian retail stores).