Lets look at the tube , its curled up and surface area of a straight tube is more
Also remember that the phosper (sp) is excited by the uv in the tube. Also the failure rate of a over driven bulb goes down hill real fast. Even at that a normal good mag ballast with a full service bulb!!!! is only about 3 months , maximzed for watts per oz of bud.
If cpl were efficent cash cropper would have them in a minute.
Along with the fairy tail of leds. (please some day by 2020 they may replace hids a florsents maybe)