You should use Western Digital RE4 WD2003FYYS 2TB.
The reason is that they do not attempt to heroically recover data from a bad sector, they will just mark it as bad. This is what you want from a RAID drive, but what you DON'T want from a desktop non-RAID drive. They are specifically designed for RAID.
Otherwise, you can get delays which will really annoy you - as the current drives have all kinds of errors and will do a lot of retries for weak sectors - resulting in jerky video.
Another concern is that if you run RAID 5, if one fails (and you do have a hot spare in place), it takes a while to rebuild, and if another fails, you've just lost your RAID array.
There are higher levels of RAID that offer 2 drive redundancy - or you can use relatively small TB drives which rebuilt in a reasonable time frame.