Tough call! Good question to think about too! I think the environmental growing conditions make the most difference in density. Sure, a larger older plant will produce larger Buds, but the question is density. Something I have been chasing myself lately . Assuming enough light is being used, and as long as the plants are sexually mature and prepared to flower, to me, the grower and his room and feed will make the difference between soft light low density Buds and rock hard dense nugg’s.
Low nitrogen during flower, higher levels of P and K and fed at proper ratio’s, under plenty of light (50 watts /foot HPS)
I had 2 runs back to back, with the same cuts, the same light, the same pots, same veg times. The 2nd run was 2 times the weight (density) of the 1st run, in the same room, in the same pots, under the same lights, only changing feed levels and ratio’s of NPK. So, other than genetics, the room your running them in and how they are feed will influence density more than the length of veg time…assuming, like I said, the plants are old enough to express sex and ready for flower when they are flipped. Everyone has their opinion, that is mine, dont shoot me over it if you do not agree…