Id go with the WD, it has worked for my ps3, dont know about the seagate tho.
Personally I would go with the Seagate. Normally I am a Western Digital kind of guy too. I had spent about 2 weeks reading about internal hard drives for the PS3 before deciding on this one.
Seagate Momentus Model # ST9750420AS SY - Used Jumper to force into SATA1
It seems that the PS3 seems to like the Seagate internals better. The main issues that I read about came from the Blue Scorpio WD series that refuse to run in SATA1 mode. If you do go WD just make sure you can force it into SATA1. That seems to be the reason for the stuttering issues people speak of. Oh yea, and you may need to use a jumper to force either drive into SATA1 (actually very easy if you dont already know how)
id go with something with 7200rpm
Here's the only true answer you're going to get regarding those two drives. Anything else is purely opinion.
It doesn't matter.