I’ve only ever worked with a 250w HPS and a 400w HPS. I noticed that with HPS, plants didn’t stay squat with good node structure. Most got incredibly stretchy. Like, I have a friend I’m helping with seeds/cuts and stuff, and with his grow, because he isn’t as savvy with understanding the plant on a biophysiological/horticultural/botanical level, and he uses a 400w HPS despite the fact I loaned him two COBs. His plants get more than double the current height of my plants as they are now by the third week. They generally look stretchy, thin, and like the plant isn’t getting sufficient light. My cousin used a 250w, and as you’d expect, it did worse than 78w of COB.