Canon EOS 40D, or Nikon D70 - for night (low light), medium shots & close-ups?

Canon EOS 40D, or Nikon D70 - for night (low light), medium shots & close-ups?

Either one with the proper lens. Need at least an f/2.8 zoom, or better yet an f/1.8 prime lens. The point is, it is the lens, not the camera that is the most influential in low light shots.

If you take a look at the pixel characteristics of each camera, the Canon has the better specs indicating that it will have less noise.
You'll need a zoom with an aperture of f/2.8 like a 24-105 which will cover everything from wide to tight close ups. If you use a Metabones Speedbooster, you'll get a true focal length of a lens designed for full-frame cameras and gain an extra stop of light. So with out the MBSB, a 24-105 goes from being the equivalent of a 38-168 to a true 24-105 f/2 lens. The aperture settings on the LCD will also show f/2 instead of f/2.8 too.

They are both oldies, and the D70 is an older oldie. If you are shopping for used cameras, a big decider is likely to be what sample is in what condition.
If you are looking at unused samples that have been squirreled away, often this are marked up stupidly high waiting for a buyer who doesn't know better.

Any will do.

Just get the lowest f/numbered lens you can afford. The lower the f/number the better for low light. If light is really low, consider using accessory lights like the flash.