Hard drive upgrade querry!

Humble request for some feed back re: hard drives
I have a MacBook 2GHz Intel Core duo
Presently has 80GB Hitachi hard drive
I know I want more storage space and I know I should have a back up.
Question is-- Upgrade internal hard drive (use old hard drive for back up) vs external hard drive as back up to existing hard drive? (As i write this am I answering my own question?-Get an external drive for backup and stay with present hard drive.) But, just in case I'm wrong, any thought/experiences regarding the below listed internal hard drives that I am considering for purchase. Thanks for any feed back that you all can give me.

250GB 2.5" Hitachi Travelstar 5K320 5400RPM SATA Notebook Drive with 8MB Cache
250GB 2.5" Seagate Momentus 5400.4 5400RPM 8MB Cache SATA
250GB 2.5" Western DIgital Scorpio 5400RPM SATA Notebook Drive with 8MB Cache

All those hard drives have the same specs. If you want more storage space I would swap the bigger hard drive into your Macbook and use the old one to back up on.

Hard drive upgrade querry

Thanks tmorgan1689,

Any opinions/experience on reliability of those drives?

Hard drives are essentially all the same nowadays. Gone are the days where certain brands were less reliable than others. I personally would go with the Seagate only because Seagate tends to include longer warranties with its drives than the other manufacturers.

Thanks for the input Kash,

Others have suggested the Seagate also.
I'll look more deeply into them.

Thanks again