Heavenly Call is right -- The Odeon has more of a bar atmosphere, and a big stage area without seats, except for some bar stools alongside the walls. The acoustics are fantastic, at least when I was there for this event last year.
There is a huge merchandise area that links the open room with the vendors room, plus a balcony offers additional seating and more vendors. Last year, I think there were more vendors at the 6-Pack Weekend than there were at ProgPower. They included InsideOut, The End, Metal Blade, Relapse, Century Media, Nuclear Blast, some independent dealers and some local vendors.
Perhaps best of all, though, there is a small snack bar with a woman who will gladly serve you reasonably priced pizza, nachos, bottles of Diet Pepsi and other snacks anytime you want.
Mike