Can the 357 Magnum LED light really support a 3x3 Closet for Veg and Flower???

Starting to purchase the items that I will use for my first grow. Was planning on buying a 400w ballast with the air cooled hood that could support both MH and HPS. If the things that I have been reading are real, this thing could support my closet and would be a lot cooler and less expensive to run. It's not cheap but I've been reading a few articles about problems with the digital ballasts too. Has me rethinking things..

Also, would using LED change any of the other aspects of a grow such as nutrient needs, how long to stay in veg and flower etc?

Just curious if anyone has any thoughts on the subject....

Ive been researching this too and the new LED information sounds promising. BUT... I think you need to use more LED panels than they say for good results. im thinking supplementary panels on all 4 walls that are as high as the buds and leaves to help the spectrum's penetrate better. but like i said, i have been researching this too lately and im not finding a whole lot. i read somewhere that a 300 watt LED has about 50 square feet of coverage. but that makes me think you would have to hang it up higher to get that square footage, but you want the LED lights to be as close as possible to the plants. Why not get 12 inch by 12 inch panels and have 1 panel per plant? I think that and having 2 to 3 panels on each wall would provide above average lighting needs. Reflective mylar? If this is your first grow i highly suggest using CO2. I have just started using it recently and i will never not use it again.