Seagate's gotten a lot of hate ever since the 7200.11 hard drive plague, and WD Caviar Blacks have less failure rates.
The price difference between the two is mostly due to the warranty. WD has 5 years and Seagate has 3. HDDs are one of the things you can't easily replace and would most likely want to take with you when you upgrade, so a longer warranty would be beneficial.
Though yes, when it comes to performance I believe they are right on par. And WD is starting to annoy me with their prices. They used to be just the same as the Barracuda's, then it became $10 more, and now the're $20 more expensive.