Pegasus2 R4 vs first gen

I edit for a small production house and we are looking upgrading some of our gear. One of the potential configurations involves the new Mac Pro and a Thunderbolt array. I've been looking at the offerings from Promise and have been leaning toward the R6. I'm a bit curious about the R4 though. It would certainly suit us as far as capacity and the price is nice, but I'm concerned with it's potential performance. I know that it isn't as fast as the R6 when both are in RAID 5, and that more drives generally leads to a faster RAID. We shoot XDCAM 1080p30 and don't do much multi-cam at all. Would the R4 work for us? Also, will Thunderbolt 2 offer any kind of benefit to the R4? Thanks.

Thunderbolt 2.0 is twice the speed of Thunderbolt 1.0, so yes, that is pretty significant. Will it help with 1080 clip playback? I'm waiting for someone to post bench marks or real world experience before commenting on that. But, Thunderbolt 2.0 will help future proof your overall system.

R4 is four drives. R6 is six drives. With RAID 1 & 5 you lose one drive's worth of capacity to data redundancy. So if I have four 4TB drives, I only get to use 12TB of storage space. If I have six 2TB drives, I only lose 2TB, so I get to use 10TB of storage space. But that is a slightly faster 10TB, that includes generating more heat, and more potential noise.

Selecting a RAID array is always a balancing act.

I'm planning on getting the Pegaus2 Diskless, using the 4TB drives in my current 2008 Mac Pro, once I get the new 2013 Mac Pro tube. That way I save a little bit of money.