Im currently using the 1500w model of theirs, its not awful but I think their wattage outputs are a bit exaggerated, Ive got 2 harvested journals and 1 coming up from different strains I did with it on 1 grow, the buds so far have been a bit airy for the most part. I'll be switching to 400w mh/hps lights pretty soon, that are actually the same price I paid for the led model.
It'd probably be better in flower if you could get them closer to the plant, and maybe the 1200 is better, but they do get pretty hot so that's not really an option. I'd say it really depends on the size of your space, mines in a 4x4 closet for reference and I'm not really that happy with it :/