Universal Prefix Argument using M-1..9 and C-1..9

[jai-bholeki via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

I am going through the documentation regarding the Universal Prefix Argument.

For instance, one can quickly set a prefix using M-1 to M-9 which call 'digit-argument'.
One can also use C-1 to C-9, which also call 'digit-argument'. That is, C-0, C-1, etc. act the same as M-0, M-1, etc.

I am writing a software that could use C-1, C-2, and C-3 but I have now started having reservations on whether it is a good idea. How often do people use M-1..9 and C-1..9
to set the Universal Prefix Argument?

A related question is why Emacs uses different keybindings (e.g. M-1..9 and C-1..9)
to do exactly the same thing, with the repercussion that users have less availability
to set keybindings themselves without affecting other users using their software
to conflict from Emacs Built-In Key Shortcuts.