as far as the kelvin scale is concerned I've found that the hortilux bulbs with the enhanced blue spectrum are about the best single bulb you can get...other bulbs have similar spectrums and probably work about the same...to get better lighting you'd have to have a double bulb or use 2 lights but I find just the wide spectrum horti grows tight nodes and hairy buds so I've never really looked much further...

Overall a mh with a higher blue content is better for veg growth and you might see a slight advantage over hps and hps for flowering and if you use both mh like a 400mh with a 600hps you should get a pretty even spectrum from seed to cure