I'd go with the Western Digital. I've always had good luck with them. And for the same price, I'd rather have the 320GB than the 250GB Seagate.
I just ordered (today) two 1TB Western Digital hard drives myself. They've always been reliable.
If you go Seagate, just don't buy the 7200.11 version of their drives. 7200.10 or 7200.12 are ok, but don't get 7200.11.
Depending on your budget, you might consider these:
Western Digital Caviar Green 1TB (energy efficient) $89
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136317
Western Digital Caviar Black 1TB (Performance) $99
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136284
Both include Free shipping as well. Not to mention 3 times the storage of the WD drive you were looking for.