So, we have stayed away from SATA for the most part, though SATA is fine for /opt/zimbra/backup and for HSM volumes.
RAID10 in principle is fine. Regardless of SAS or SATA, I would spring for the best hardware RAID controller you can find, with a lot of onboard cache and battery-backed as well.
With the config you describe, you might do just fine with SATA--most of the time. But when the server starts getting hammered...
Also, we look at servers having a lifetime of five years. So, when you amortize the higher cost of a SAS vs. SATA disk subsystem over five years, the extra cost per year, or even per month, is very small. SAS/SCSI over SATA just seems like cheap insurance, so that's what we do.
Hope that helps,