IMHO I don't think that the fact that both endpoints of this SATA connection are from the same vendor (Marvell) makes any significant difference.
Intel claims that the max performance of your Intel 510 120GB SDD is 450MByte/s, so a good performing 6.0Gb/s SATA connection is essential. You should check which type of Marvell SATA your P8Z68 board has and if that is the same controller that the forums describe. A couple of forum post are talking about older Marvell SATA controllers.
The easiest thing if you want to be sure is to perform some benchmarks yourself: the SDD connected to the Intel or to the Marvell port (be sure to install the latest drivers for a good comparison).
Sure, I guess try both, but does anyone think the Marvell is going to be faster than the on-die controller? I highly doubt it. More importantly, Marvell apparently doesn't support TRIM.
"If you are using a SSD use the native Intel or AMD SATA 3Gb/s or SATA 6Gb/s ports, I advise that you do NOT use the Marvell ports for your SSD, they do not support TRIM, they are capped at ~375MB/s and deliver very poor 4K read and write performance compared to the Intel and AMD SATA 3Gb/s and SATA 6Gb/s ports. I also would suggest you not use the Marvell ports for your HDD either. Only the DVD drive if anything. If not just disable it in the UEFI/BIOS to cut 2-3 seconds off your boot. Here is an example of why the Marvell ports are trash."