For my money, I'd do two three-disk arrays, with one shared hot spare.
If you don't have an need for a single block of space larger than a 3 disk array, then there is no reason to cram all 6 disks into 1 raid. You're not going to gain anything in performance or over-all space, and, given a two disk failure, you're probably going to be in a better place.
@Dayton Brown: The total space will be the same...3 1TB drives in a RAID5 is what, 1.8TB? 6 will be 3.6 by the same measure, so in that sense you'll have more space in that particular RAID volume, even though the total space will remain the same. The difference is, RAID5 only allows for 1 parity drive, whether there are 3 drives in the RAID or 300, so splitting the drives into manageable groups adds protection against multiple failures. Even if you lost 3 disks, for example, you'd only lose half of your data.
If you moved to RAID6, a six disk array would make more sense, because you could lose two and be okay. But most people jump straight to RAID10, and skip 6.