IMHO, unless going vertical I get better coverage running the 600's, for sog or wide spread------you just need to run more. Less heat and closer to the tops too, imo. The bulbs...yeah, they cost as much as 1000's sometimes more, because they're not as 'popular' but I really like my 600's over the 1000's and I am in a 12x12...... Remember, it watts per sq ft.....the 600's spread out better. Seeings how most growers seem to prefer the 1000's, keep seeking opinions.
Great luck to you in helping your friend's build!!
gman