WINDOW AC-Vent to bedroom or attic?

I have the option of venting my AC window unit out into bedroom side of growroom or out into attic. The attic gets very hot of course and the bedroom gets hot but not as much.Im thinking 120'degrees(attic) versus 90'(bedroom)at peak of day.
Is it ok to vent into such high heat?Will it be cooler in growroom if I vent toward bedroom?

I could be wrong about this but I think all air conditioners intake air from the room they're cooling and vent hot air to the outside. Pretty sure about that, a/c's have a screen filter on the front, near where the cold air comes out. I would vent it to the attic since it's only hot air coming out. Take a look at your unit, no, not that unit, I think you'll find that's how it works.

http://www.icmag.com/ic/showthread.php?t=95491

cheak that link out