Rod: most people I know use HPS. I know a couple of people who have used Gravitas side by side with HPS, and yes there is a difference, but if you are starting out the cost is nowhere near worth the improvement in yeild. You are much better off buying more HPS lighting. I don't know anyone who uses LED, and although it is getting better, it's not quite there yet. All the big house busts you see still use HPS. Maybe it is old school, but they are cost effective and do the job. Just my two cents. If you are rich and want the best homegrown for personal, maybe get a gravita, otherwise get more hps