I keep hearing MH and HPS are not the same spectrum. Now were is the difference between lets use for example: say a 250w HPS 6500k and a 250w MH 6500k bulbs? The color are the same, the wattage is the same, and the luminance is going to vary between manufacturers anyways.
Just using it as an example. I know you can get lower (2000k) spectrum in hps, Is that what the plant really needs?
Well it's an example of something that doesn't exist. The plant needs bluer-spectrum light during veg stage, that's when you use the MH because that is what it gives off. The plant needs redder-spectrum light during flower stage, that's when you use the HPS because that is what it gives off.