I've seen people argue that if the light has an SOS mode for emergency use, it needs to be easily accessible, which means putting it early in the switch sequence. Similarly with "tactical" strobes. As such they can get in the way.

On the other hand, the Photon Freedom has an SOS mode which is so buried in the user interface that it almost might not be there at all. I find it hard to get to, and hard to remember how to get to it, and hard to distinguish it from the 3 other strobe effects it has.

There are some advantages to making it a function of the software rather than just putting your hand over the light. One is that it lengthens the battery life. Another is that you can leave it switched on strobe/SOS even while you sleep or are otherwise occupied.