Hard to say for one light, 600w are more efficient on electricity. Like 3 600w would be more efficient than 2 1000w because its lower wattage and cheaper but you get better light distribution.
The biggest factor, especially with the hydro hut, is how cool you can keep the light.
1000w light is always going to give off more light, but you lose intensity with distance, so if its properly cooled and you can keep it 10-14 inches from your plants then you will get bigger denser buts, especially if its SOG you will get deeper penetration. If you have any heat issues, or if you worried about power, the 600w will be more efficient. 1000w HPS light pulls 1125w with ballast.
As far as yield, theres too many factors, the strain, the style of grow, the nutes, a million factors. Its hard to compare watts to grams. I would say .33-.5g/watt is what most amateurs would get, It really depends on the strain, 1g/watt would be a pretty damn good yield for any grower!
Again theres a million different factors, some people say they can get 6lbs with 2000w growing vertical, others have achieved amazing scrog results with 1000w lights.
