-b in checkout is short for "branch" while -c in switch is short for "create".

IMO the UI of git switch is much more intuitive, since the argument is always a branch and the default behavior is to switch to an existing branch. For slightly different behavior (like creating the branch first) there are flags.

So I think it's good that the flag for switch is a different one than for checkout, since the interface of git checkout was quite unintuitive IMO.