Well this is one of those questions that comes up often enough- I'm sure if you looked back aways you would see the same general question asked over and over again, but oh well.
From what I can tell, it is mainly a personal preference people base of their previous exp with the different drives, and different people have had different exp.
Some like maxtor, some seagate, and some WD.
I have seen more complaints about maxtor though than any other, although I have read some good things aswell.
I personaly use seagate and have been for some time and have had no problems with them, main thing with them is reliablity and lack of noise.
The WD cashe monsters on the other hand are great drives but a little noisier, so it is just a traid-off.
All the drives are close to the same price so cost shouldn't matter too much.
As a suggestion look as storage review, they have some good info about the different drives.
Emrys