I sprouted a few seeds about a month ago. I tossed them under a T5 for 2 weeks and then into 2 gallon bags under a 600W MH in a 3x3 for 2 weeks and they are already creeping roots out the few bag holes. I dont know how you guys grow a full plant in a 3 gallon pot! I am going to throw my ladies in 5 gallon fabric pots to let air pruning take care of the roots. Anything smaller than 5 gallon fabrics are a waste, IMHO.
I loved the CMH but I ended up with airy buds for two grows, because the heat was tough to control on a dual bulb 630W CMH with no dimmer inside a 5x5 tent and even with venting in cold air, 20°F, from a window in the winter. Would probably be great in a more open area but it was running hotter than my HPS lamps, because the CMH was an open hood fixture and the HPS hoods I have are air cooled. Great quality and flavor from the final harvest, but they just didn't have the density and I think it was from heat stress. Regardless, the girls were happy under the CMH and didn't show any stress other than not bulking up.
My main fear is that an HLG Scorpion will generate more heat in a 5x5, when compared to an air cooled 1000W DE HPS, forcing you to use more aggressive cooling, and causing higher total energy consumption, even though the Scorpion is much more efficient.