Every plant can only reach it's predetermined genetic potential. Your not making a plant any better by adding more light or nutrients,etc. Rather you are allowing it to reach it's genetic potential! That being said, I like to look at all these "factors" as "limitations" that will prevent you from allowing your plant to reach it's genetic potential.
Providing your plants with optimal light is important, not supplying enough will limit your plant from reaching it's full potential.
Providing your plant with the right amount of nutrients is important, not supplying enough will limit your plant from reaching it's full potential.
Providing your plant with adequate root space is important, not supplying enough will limit your plant from reaching it's full potential.
You see where I'm going with this? Every factor can limit your plant from reaching it's full potential, hence why we try to give our plant optimal conditions so in return we can get a plant as close to it's genetic potential as possible.
Yes, the sun has the "ability" to grow larger plants then a 1000w but there are also a bunch more factors that can come into play. I've seen massive cola's using 600w's & 1000w's so you may want to consider other things besides just your lighting.
Temperature, Genetics, root space, Humidity, PPM, PH, Veg time all play a role in your final product, and if any one of these are not in the adequate-optimal range it can really effect your harvest.
How high from the canopy was your 1000w and what were your grow footprint/dimensions ?
How long did you Veg for?
Vegging longer and training will dramatically increase your yield. Generally people who grow outdoors, use fewer larger plants by Vegging longer and Indoors people usually have lots of smaller plants for more harvests per year.
