Looking for a good Nikon or Canon camera?

I'm looking for a camera that does great in low-light or night shots, as well as does great when taking photographs of stage plays, w/o a flash (don't want to distract anyone).

Any recommendations? I was hoping for a mid size camera, around $300-$600. Preferably able to buy different lenses to attach to the camera. By the question: a Nikon or a Canon please, thanks for your help!

Nikon D3100 kit.

You can go with Canon Dslr Camera…