600 or 1000w

I am debating on getting 2 600 or 2 1000w for flowering. the most i will be flowering at a time will probably be 24 plants. any suggestions? I know more light is always better but when does it become wasted energy? Heat isn't to much of an issue as they will be air cooled reflectors and good ventilation.

The best way to answer my question would be:

The average number of plants you can grow under (1) 600w is ________.

The average number of plants you can grow under (1) 1000w is ________.

god dayum thats good enough. I would get a 1000 definitely around a 15 square ft area each

maybe more