We are rigging the SC15 jib sheets with a Ronstan and a Harken, one in each side. I prefer the Ronstan due to better grip (line suffers more, though), efficient cleat, less weight and lower price. It is early to say anything about durability.
If buying new ones I would use price as the first criteria. You should choose Ronstan if the crew´s hands are not strong (teen, woman, etc.)