Yes, photosynthesis is important. But on my previous grow I simply did not have the space for 8 plants in the armoire with full leaves. I needed better light penetration and air flow. So I would trim heavily. But I also added CO2. With the CO2, they would recover from the trimming in one night and by the end of a week would be just as bushy again, and require trimming.
So, I personally think the difference is CO2, if you need to trim for whatever reason. To be certain, that there was no loss in overall production, of course, I would have to run two side by side. But as I said, plants are tight inside armoires, and light and air flow is very important, too.