If your PC only has one or the other, you don’t really have a choice — use whichever Windows Hello method is available to you. If it has both, then you can actually use both.

Windows Hello facial recognition no longer works in poorly-lit rooms This is due to a move Microsoft made to shore up security with the feature The change to require a ‘color camera to see a ...

The newest revision of Windows Hello Face requires a color camera to authenticate logins in addition to the use of IR sensors, somewhat limiting the function's usability in low-light scenarios.