When I grow donut I get 2.3g/w when I grow walls I get 1.2g/w but twice the growing space for me either of those is a very valid reason the 3 day veg is just a bonus.
I grow between 12-24 plants each time depending how I intend to run it and use multiple hps either 400w or 600w, normally I grow hydro but I also like to grow organic compost handwatered.
Not all strains works so well vertically, you will generally take more from a proper vertical grow system than from just putting plants round a light with lamp in the middle and not all vertical systems are equal.
I have several friends that grow the same way I do and none of us would ever go back to horizontal growing as it's just far too inefficient some of my friends are pulling 6 grows a year back to back but I prefer to take time off especially over summer.
Vertical growing needs a good environment to do well and is probably less forgiving than horizontal.