Actually, the models with the B120i controllers also support SAS - but only non-hotplug drives. Also, the B120i controller only supports RAID 0, 1, and 1+0.
So in regards to SAS support -
ML310e Gen8 w/ B120i embedded controller = non-hotplug SAS, RAID 0/1/1+0
ML310e Gen8 w/ SmartArray P420 controller added = hotplug SAS, RAID 0/1/1+0/5 (can add also RAID 6, RAID 6+0, RAID 1 ADM, and RAID 1+0 ADM support by purchasing Smart Array Advanced Pack 2.0 license)