So say hypothetically I was working with 20x 1000 watt HID lights in 600 sq ft am I better off growing 40 r 50 big tall guys or several hundred smaller plants? Would yields differ greatly?
Well, I hope you're using less light that than, because you'd be reported by the electric company for having a consistent $800+ electric bill. Unless you're growing in a warehouse, 20K worth of lights is way too much and will draw lots of attention.
The advantage of a sog setup (100s of small plants) has is that you can take clones and drop them immediately into flower after they've rooted. It has a high plant count, which is bad, but a faster turn around and doesn't require separate lights for vegging, which is good. Sog usually has a higher overall yield per square foot than larger individual plants because you get more top colas per square foot. With scrog, you can turn multiple colas on the same plant into top colas by spreading them out horizontally.
If you really want to maximize yield per plant, go for a scrog setup. About 1 plant per square foot. Lighting should be very close to the top of the scrog, and you're shooting for about 30W per square foot. You can use smaller wattage bulbs to get closer. A 150W HPS can be about 3" away from plants without burning them if you have reasonable airflow. For tall plants, or a sog, you'd need about 50W per square foot, but with scrog you gain a lot of efficiency by having so much more of the plant right by the light. Also, it keeps the plant count down versus sog which requires a ton of plants.