In theory, it shouldn't make a difference. Each sensor has a certain absolute sensitivity threshold, and as long as there is sufficient light to exceed that threshold, the sensor works. It's worth noting that the center point is usually more sensitive than the other points, and the specification for the overall sensitivity of the AF system is based on that center point. It's also worth noting that not all specifications are created equal - both the 5DII and the 7D have the same -0.5 EV spec, but in my experience, the 5DII did much better in very low light.

But that's theory. The other practical factor involved is contrast. The AF system needs not only a certain absolute light level, but also a certain amount of contrast in the subject to detect the phase difference. To the extent that the additional light from a lens with a wider aperture allows better detection of the contrast, it should mean less hunting.

In very low light, enabling the 4 or 8 point expansion can also help the system lock focus, if not at the exact spot you intended. Note that expansion will use the immediately adjacent points, even if you have it set to manually select only cross-type points.

Realistically, empirical testing is probably the best way to figure out what's going to work best for you, and it sounds like you're already doing that.