The vim version is much easier, if you ask me: 3 strokes, 2 keys and 0 combinations.
The one you suggest however requires 4 strokes (ctrl then o then shift then s), 4 keys (ctrl, o, shift, s) and 2 combinations.
The "cc" sequence deletes the line and switches automatically to insert mode. To forgo the switch, the sequence then becomes "dd".
Maybe I have my bash/readline vi mode configured specially to do this, but if I want to delete the entire line and type a new one (from anywhere in that line), I do something simpler than either of these alternatives:
<esc>S
Esc exits insert mode (of course) and capital S erases the line and puts you in insert mode at column 0 (just like in (n)vim, right?).
Like I said, maybe I configured that? But 'S' is standard vim-stuff... (I'm not able to double check my config at the moment).
[Edit: right after hitting submit I realized that my way is perhaps "arguably" simpler because I do have to hit shift to get capital S. So I'm also hitting three keys...]
<c-o>S is also a vim sequence. The equivalent readline/emacs is <c-e><c-u> or <c-a><c-k>, or just <c-u> or <c-k> if you're already at the end/start of the line.