I know im jumping pretty far back here but had to chime in lol.
As far as yields in the system, I've pulled upwards of 3lbs a light in RDWC using doubled ended HPS. Setup wasn't cheap though... Tons of AC/Dehumidification and Co2. Every aspect of the environment was dialed in.
As far as LED, I've always believed it was a matter of time before they get there and I think if done properly as far as CCT selection/combination they are finally about, if not already there, with COB setups. Cree is releasing their CMA Arrays with "Fidelity" binnings up to 98CRI. Overall I think it says 20% gain in effeciency over CXA2.