Earlier quoted context omitted.
The difference for me was realizing that Shift-V % will typically highlight precisely what I want - though that's a bad example, visual mode is rare for me. More frequently it's something like `dap`, which works with a level of precision across lines that aren't necessarily all on screen. If I click and drag, I'm liable to select one extra or one less line, e.g.
Is this better than using the keyboard with arrow keys and ctrl/alt/shift?
I guess if you include chords of modifier keys, you could have 2⁴×4 possibilities, which would be extremely competitive with vim in this regard, although I haven't encountered an editing environment that did that. (That's not to say that it couldn't exist.)
I consider myself a proficient but unsophisticated vi user, and I seem to have at least 19 cursor movements that can be combined with selection or deletion in my muscle memory, in the sense that I would regularly use them without being consciously aware of how I chose one movement command rather than another. And that's not counting the ability to prefix them with repetition counts, which is usually a more conscious activity for me. I know that vim provides another dozen or more that I've never learned well, but it seems like other people have.
It does take time to internalize these, which is one reason we see so many people making "learn vim" games and tutorials. And I could imagine that they might not be the exact selection of movements that someone would find optimal, let alone easy to remember or articulate.