I semi-recently switched over to LED for flower and I am getting the same (or slightly better) yields with my PhotonTek x600 watt pro LEDs (630 actual watts iirc) as I was with 1000 watt single ended HPS bulbs in air cooled hoods. And I run them at 3/4 power (450 watts or so) in early and late bloom (usually something like the first 1-2 weeks and last 2 weeks, so almost 1/2 of bloom).
You definitely lose heat though, which can be an issue in the winter for sure. I need to use oil heaters in my room.
And I feel like I battle more nutrient deficiencies vegging with LED’s than I did with metal halide or t5 fluorescents.
Especially magnesium deficiencies. Also light stress. But I’m still getting used to them. I used metal halide and fluorescent lights for veg for like 15+ years.