Anandtech has a good writeup I found the other day regarding the issue:
http://www.anandtech.com/show/2973/6...-intel-x58-p55

Looks like the Intel controller is only marginally(2.4%~5%) faster at everything except sequential read performance... Essentially a tossup.
Intel’s X58 still has a few tricks left up its sleeve - it manages to be a very high performing 3Gbps SATA controller. Other than in sequential read speed, it’s even faster than Marvell’s 6Gbps controller with a 6Gbps SSD - although not by much.
I'm not even sure if I care so much about 80 vs 78mb/sec random read performance or 137 vs 129mb/sec random write performance, if I'm getting over 100mb/sec more sequential read performance. That's what that review really seems to come down to...