411 Needed! Digital ballast's question!!!!!!

I posted in another forum as to which light is going to be best for my room,as ive decided to go towards a 1000w HPS(for some insight,this is a strictly flower room 5x6x8)...i was torn between a 600w and 1000w and like i said i decided on the 1k,BUT...doing some more research ive come accross people talking about alot of 1000w digital ballast's are still kinda unreliable and could use some more engineering,whereas the 600w are pretty much bug free..now some of these posts ive read were a few months to a year old,so that is where my question lies...

are 1000w digital ballast's good now or would i just be as good with a 600w? what is going to be the power useage differnce and the yeild difference in the two aswell? this is a 4-8 plant setup btw

nevermind,going with 2 600w digitals,i got 2 plants ready for flower,im going to get one 600w to finish these off then next harvest will be 4 or 6 plants under 2 600w....

strain is satori,what do you think i could expect as far as yeild with these 2 plants under 1 600w? plants are around foot and half to 2 feet tall and been vegging for 2-2.5 months and are stacked,in other words looking really good and potential to get massive