There have been a lot recommendations for the Western Digital Caviar 640GB 7200 RPM 16MB Cache Hard Drive over the Seagate Barracuda 500GB 7200 RPM 32MB Cache. They are both price around the same with the WD being a little more. I’ve read some posts where people swear by the WD speed and price per GB ratio.
Since they are both made by reputable company, wouldn’t the Seagate with the 32MB Cache be a better and faster hard drive than the WD leaving the 140GB extra aside?
Why would you say "$10 more, nice!" and then ask whether or not it's an advantage?
There's an in-house article that shows some benchmarking and pointers on HDD cache: Tom's Link.
The difference between 16MB vs 32MB of cache on these harddrives is something you'll basically never notice. Yes, it's good to have more. Just like it's good to have more RAM and more Megahurtz floating around everywhere. But it doesn't mean it's something you should stress. See the above benchies, here at Tom's, the difference between 8mb and 16mb was basically none; so the difference between 16mb and 32mb is going to be even less, or completely not worth your extra $10.
That said, the 640g WD at NewEgg is $75. That's the one I'd go for.