1000w dimmed at 60% or 600w hps bulb.

Which one would be more effective and which one would me more efficient(energy wise). I'm planning on finishing this harvest at 600w(what I originally been using) since I just barely bought this new 1000w dimmable ballast /bulb today and I'm in week 6.5(don't think using a 1000w for the last week or 2 would make a difference on buds other then my energy bill lol) so idk if I should just keep running my 600w hps or dim down my new 1000w to 50%-75%. Which would get better penetration and coverage? I will be using my 1000w at 100% power on my next run for sure

It's more efficient PPF (or even lumen) wise to use 600W bulb/ballast that have 1000W bulb/ballast@600W.

Check the documentation of your ballast manufacturer.

Dimming the ballast affects the light spectrum of the 1k bulb. Its meant to run at the correct wattage for optimal performance.