Need a new Laptop Drive

OK, I got a new used laptop and putting some higher end stuff in to make it the best it can be for a Core2Duo based. I've gotten the proc (T9550), RAM (2x4gb PC2-6400), etc etc and now it's time for a hard drive. Firstly, SSD is out due to price/storage expense and I have only one place for the drive and need room.

Here are the contenders:
For Seagate, I'm looking at their Momentus XT hybrids model(s) ST95005620AS or STAN500100 (retail box) - both 500gb
For Western Digital, the choice I'm deciding is Scorpio Black WD7500BPKT (750gb) or WD5000BPKT (500gb)

What is everyone's EDUCATED (read as please no random "WD sucks, they f-ed my RMA up") opinions, I've done a bit of research on these, and the XT looks to be ahead of the Scorpio Blacks, though I recently saw the XT's were getting some firmware upgrades due to issues over time with the drive. Anyone have real world with these drives, or know a good comparison where they put the SB's against the XTs? I saw one and the XT beat the 500gb Scorpio Black, but the 750 wasn't out at the time and it's always good to have 2nd and 3rd/4th/5th opinions!!   I don't have a pref between 500gb vs. 750gb, and put the WD 750 in for reference and comparison against the other drives. If it's better, fine. If not, 500gb is enough space for me...

If you think there is a better contender, please let me know which one and why. Has to be 500gb+.

Thanks all!!