Gil-
There could be a number of reasons why this hold true. First, latency is not as low with the SF SSDs. However, depending upon your cache capacity the latency of the SF drives could be irrelevant. So lets start with how much cache (4 GB?) and also, more importantly, which motherboard?
If your motherboard has the NF200 that is going to probably be the culprit. I had to switch from the E759 to the E760 specifically because of the NF200. While it multiplies the bandwidth, it adds serious latency concerns. To test easily, place your raid card in PCIe Slot #1, your board will boot with the GPU in other slots. I know this can be a pain with Dual and TRI-SLI. However, if you have the NF200 you should see a tremendous drop in latency.
Remember, a slot with x8 without the NF200 is faster that a x16 with the NF200 when it comes to raid cards!
Please reply back and let us know how your results turn out! Very interesting!
Thanks for reading,
Paul Alcorn