hps for sure,,, use halides for vegetative,, how many plants u plan on growing????? Im using a 400w switchable ballast, and its perfect......low cost and and heats easy to maintain.....
man if u plan on doing 20,,, ull b straight with a 1000w,, b ready to pay loot tho for that electricity,,,, that should be perfect for good yields and quality,, good luck
I think its possible to get the same yield from both your ideas. The plants do still use blue light during flowering just not as much as needed in veg. But for practicality and price i would go the 1000w HPS. Peace