@b0rk an interesting nuance, which you can see in these replies, is that the choice of base largely depends on which of the two typical uses for fixed point that you're discussing.

For financial calculations, you'd typically use a power of 10, because accounting regulations about rounding are written using that language.

When you're trying to wring decent real-number performance out of lower-power hardware, it's more typical to use a power of 2, so you can use shift to divide.