I understand what you are saying and I understand what you see as being logical but look at it in another way. One layer of roofing shingles is all you need on your roof so would there be a value in laying down a double layer? It would give you twice the protection using your logic, which is more has to be better, so would it be a value to you do to it?
If you were painting a wall two coats will easily give you all the coverage you need so would you give your wall four coats of paint just to make sure it has all it can possibly get? Would that be better and would it be a better value? If more equates to better, as you seem to believe, than I have to guess you would say yes, you would put on four coats.
Doing something right is one thing and doing it right is a value. Overdoing something is not making it more right or making it better and overdoing something is not a value.
By the way you said; "a lot longer than your botany degree." I do not want to mislead you so I will set the record straight. My brother in law, my sister and my niece are the ones with the botany degrees, not me. I only know what I know by having been taught by them.
I always say when it comes to growing for things other than water and nutes a more than is actually needed is better than not enough of what is needed. I always say it about pot size and I say the same about lighting but there is, in my opinion, where you reach a point of diminishing returns, where what you pay for what you buy and what you pay to operate it does not give you enough of a return to be worth it. Having a little more than what is needed is not at all a bad route to take, it is not an injudicious decision to make, but having a lot more than is needed is illogical.
As I said in my original message between your two options I have to say I would go with the two 600 watt lights, to me that would be the better option of the two so if your mind is made up that those are the only two viable options my vote is go with the two 600 watt lights BUT I still believe it is a case of having more than your plants will actually be able to use light-wise. But if it is a value in your eyes that is all that matters so by all means go that route.
I am sure that you would never consider this but given the size of the area you are talking about using you and the amount of money you are willing to spend you could go with lower wattage HID lighting and buy a number of LED light bars and mount them on portable posts and surround your plants with them and put them between your plants and flood them with absolutely nothing but the light spectrums the plants will use and they would hardly put off any heat and they would use very little energy.
Several years ago I followed a thread in a grow forum on another herb site and the member did an all LED grow. He had what may be the thickest most lush fullest heaviest producing plants I have ever seen. All the way down to the lowest branches he had big thick heavy hard buds. His plants were totally flooded with light but in only the light spectrums that the plants actually use and he did not need an expensive elaborate ventilation system and his electricity costs were minimal and nothing that would ever draw the attention of LEO.
So if you have so much money to invest into your setup you may want to sit back and puff a bowl and rework some numbers and consider doing something of a combination of what you have in mind and what he did if you really want optimal conditions for your plants to grow in.
