Hi there kc kong, as you well said it really depends on other factors, for instance, in a 1sq meter tent I wouldn't go 12/12 FS and in a pc box I wouldn't veg for two months. But lets imagine that you mean if there is a difference between 12/12 FS and vegging, I would say yes, there is a difference because if you veg the plant will get bigger and therefore she will yield morehow much will a plant yield if you start it at 12/12? I know it proly depends on a ton of things but whats the average 12/12 plant yield?