400w or 600w?

I have this darkroom twin and I already have the T5s for the top but I'm not sure if I should use a 600w or 400w hps/mh light because its only 3x3 so I'd say at max I'd have 5 plants in there. I have some fans and a filter though smell isn't a huge problem.
Just looking for input. I know I can get decent yield with 400 but would the 600 be worth the extra cooling?

A 600 puts out double the light of a 400 and if you bought a cooltube heat shouldn't be an issue either way. A 400 would work pretty good in that space but you will probably want to upgrade sometime down the road, just save yourself a step.

600! you will be grooving man and with 5 in there you want all the light you can get a 400 w has 24 inchs of good strong light while the 600 has 36

the answer to this is always:

Get the higher wattage.

Look at dimmable ballasts. You can get the 600 and run it at 400 if it gets too hot.

600.
I'd be preaching the 1k'er to you if it wasn't for the 3 x 3.
600 should suffice.

i get just as nice tops and yeld from a 600w as i would a 1000w, but heat played a facter in my grow room too.

I would go with 600W. More bang for the buck.

Gotta say y'all I would get the 400. Not like you have much height there soooo your not going to gain much by cramming extra. A 400 has the spread. You're not going to grow big tall plants in there subtract a foot for the hood and filter a foot away from the light a foot for the pot what do you have left 5 24" plants loaded with 12" Colas. That's 5 feet there, how tall us your space. Be smart and efficient.