Assuming the pot is big enough, you get a bigger plant, lol.. fill a bigger space.
Is it more efficient to do smaller plants and greater quantity? Yes, up to a point, but not every decision is about what is 'best'. Sometimes it's just what you prefer or want to do. Just as some people use inferior substrates that come with more risk or impede roots more than necessary etc etc. Yield is not necessarily better with a bigger single plant vs many plants. that would be user-error caused. Indoors with ambient co2, no matter how you do it, the rough ceiling is going to be 50-70 grams per sq ft. CO2 is the limiting factor. It is the backbone of nearly every molecule the plant must build or replicate for maintenance, growth and ripening... so, law of conservation of mass applies. less available carbon = less growth in all normal contexts.
I could shave 2 weeks off my vege phase by doing a SOG and maintain my yield. I don't want to deal with 2-3x as many pots. That comes with more work and i'd have to remake my irrigation system and buy smaller pots etc etc... too much of a pain in my ass to save 10-15 usd/year. I don't use my big lights until the last week of vege, anyway. So, 2 fewer weeks while using lower-wattage lights is not as big of a savings as most think. Also, i don't grow year round so saving a week or two of time doesn't add value for me. Individual context matters.