At LockerGnome.net, tg1998 asks:
This is an interesting question, and the best answer depends entirely on what you plan to use the drives for. A RAID configuration can certainly make the most of your three hard drive option as it would allow for redundancy on your excess storage without driving down the speed of your primary operating system disk. You could load your operating system and program data on one drive and create a redundant RAID configuration on the remaining two. This gives you quick access to your programs without the slight slowdown present in redundant RAID setups.
There are tons of different RAID options you could go with. Some of them would work great with two larger drives and others would take advantage of having three physical drives. Ultimately, I’d say you should be fine with either. Having three drives means less data loss in cases where one drive fails. A single arm misalignment can destroy an entire platter worth of data and render your drive fairly useless.
I’d personally avoid RAID 0 at any cost, especially if you opt for the two-drive configuration. RAID 0 might result in improved speed, but a single drive failure will render your data unreadable on both drives. This configuration is typically used in conjunction with an additional RAID layer. RAID 5 (block-level striping with additional parity) required three drives to work and can give you a performance boost and the ability to survive a drive failure without data loss.
You do get a slight space advantage to having two drives, however. It’s easier to cool two hard drives than three, and not all cases have the bay space to support more than two drives. Some slim-line cases only support one, with many users being left to jury-rig space for a second. This isn’t likely the case with your setup, however.
Whatever your choice, just remember that hard drives can fail at any time. It’s often better to hedge your bets and offer additional redundancy to your critical data than put all of your eggs in one (or two) basket(s).