It would seem that there are daytime (daylight) signals and nighttime signals (dark). In general, the daytime signals simply won't work well in nighttime, and vice versa.

Signal mirrors and "large" brightly colored objects would fall in the daytime signal group. I like the passive nature of brightly colored objects, but the "large" requirement makes them more difficult to carry than a quality signal mirror. The signal mirror requires some knowledge & experience for effective use.

Strobes, flashing flashlights (headlamps), and laser signals would fall in the nighttime signal group. I like the non-directional character of the strobe - in comparison to the directional character of most flashing flashlights and laser signals, but the strobe doesn't have the multi-use feature of a flashlight. I've never been fully comfortable with the laser signalling devices (I have one), but in years past Doug Ritter has spoken well of them. Has anyone else here done some personal testing of laser signals?

In the end I tend to think folks need to carry BOTH daytime and nighttime signals even if carrying a personal locator beacon (PLB) in order to facilitate getting found.