Low-light performance is how much usable detail a camera keeps as illumination falls. It depends on sensor size and pixel size, lens aperture, noise processing and shutter speed. A camera that brightens a scene with heavy gain produces a visible image that reveals little.
Night is where most security incidents happen and where most camera selections rest on a number nobody can compare. Look at recorded footage, not the datasheet.
The physics that set the limit
A larger sensor and a wider aperture gather more light. Packing more megapixels onto the same sensor shrinks each pixel and generally hurts low-light detail.
Judging a camera honestly
Ask for a sample recording of a moving person at the distance you need, at night, with the lighting the site will actually have.