crowding or low temps-which is worse?

[applefalls]

I have 8 chicks (EEs, BRs, red stars, and buff orpingtons) who are 7 weeks old. They are crowded in their playpen, so we try to let them spend their days in the tractor and outdoor run. We have no electricity out there, so at night we've been bringing them back inside to their 6 square foot playpen.
During the day, we've had temps in the 70s and 80s for a few weeks.

With unseasonably low night temps this week and last (tonight is supposed to get down to 38 degrees, but most nights have been in the 40s), I'm wondering which is worse: overnighting in low temps outside or being crowded together inside all night?

 

[jennmugg]

My girls crowd together every night no matter what. Crazy birds

 

[applefalls]

Mine huddle together, too, when they sleep.
When I say they are crowded, I'm talking about when they wake up and start complaining that there is no where to stretch and play.