Consider the following situation: ($CH\perp AB, H \in AB$).
I was always wondering if we should write that $CH=h_c$ or $CH\equiv h_c$. I am not sure which one to use when I am writing my solutions. Which one do you prefer and why? If $CL$ is the angle bisector of $\angle ACB$ ($L \in AB$), should I write $CL=l_{\angle C}$ or $CL\equiv l_{\angle C}$?
Here $CH$ and $h_c$ are numbers: they are a length of an altitude.
Thus, it's better to write $$CH=h_c.$$
If we want to say that points $A$ and $B$ are the same, so it's better to write $$A\equiv B.$$ By the way, we can write $$\{A\}=\{B\}.$$
I think, all these are not so important. We always know from the context about what we say.