More lights are far better even coverage to utilise more overall intensity and not fry things. In a 5x5 4x cmh would be nice if you want to run bulbs, might be the wiser option if you are in a cold year round country.
For led and cob you have lots of choices but the same principle applies, low W units spread across the entire space as much as possible. 1200W of cob/led would be no joke in a space that size, comfortably passing 3lb with the right strain and attention. You can drop down to 800/1000W of led if money is currently an issue and still easily pass the 2lb mark with a run of the mill sog net set-up. Cobs and leds still send a shit ton of heat into the roof area so make sure you run an 8" out take, directly above the centre of the space to suck the hot air off the units and protect them from summer time over heating.
horticulturelightinggroup.com
