2 circuits connected in one box?
It just seems like you have two 3-wire cables (with constant and switched hots) going into and out of that box, along with a 2-wire constant feed. It's not two circuits. The reds are switched and the blacks are constant hot. 

IMO I would pigtail each color and use the side screws on the receptacle just like they were before. 

That looks like #12 so you can no longer use the backstab/quickwire holes in the back of receptacles (in the US at least).