Think a bit about what lenses you want rather than what body you want. If you are talking low light, you should be looking at prime lenses rather than zooms. Nikon, Canon, Olympus, Minolta, Pentax....they all made perfectly good bodies, but what kind of lenses do you want? For me, a fast 35, 50 and 85-100 is all I need and I have small hands so that pointed me toward Olympus and Leica for their compact systems and quality, fast lenses. The Oly lenses are also adaptable to EOS cameras. I have an EOS Elan 7 and is a great camera especially with a 50mm 1.8 or the 85mm f1.8. I don't like the 35mm offering and everything is so big to accommodate autofocus.
So what is best.....depends on what you really want. Pretty much anything that is in good condition with a 50mm lens will preform better than I'll ever need!