Bigger tent bigger yeilds with 600?

[JH420]

So I keep hearing it's about watts per sq ft and that 3 x 3 is the right size for a 600 (horizontal air-cooled)...lets say you do the fairly common 1 plant per sq ft so 9 plants in a 3 x 3 tent...would you not yeild more in a 4 x 4 tent with 16 plants? Or even 9 plants in a 4 x 4 as the plants will have more space to bush out? Or is the 600 watts the true limiting factor and all set-ups will yeild the same (I doubt this, but that's what most of the info out there implies).

Please vote twice if you think that both 4 x 4 setups will yeild equally...(assuming you give extra veg time for the 9 plants setup vs 16)

Thanks in advance for your input.