I leave some on a second year vine if it's big enough. So vine size is the key in my opinion. As with all young fruit vines/trees, I thin extra heavily. So how big is your vine? What is the caliper of the trunk? How big and long are the canes and how many did you leave? How many sq ft would you expect the vine to cover this year? Is it in full sun?

These are the factors I'd consider.