RAID 0 should be faster, as an individual standalone SATA III spinning disk will top out at about 150 MB/s.
HOWEVER – Setting up a RAID 0 with 2 drives in a toaster is BEGGING for disaster. Like, knocking on Disaster’s door with a giant hammer. Don’t do this.
I’d suggest investing in a new enclosure with at least 3 drives for a RAID 5 setup, and keep the original drives as backup.