1. Even in those situations, I believe a veteran vim user would still beat someone using a mouse.

2. That said, the situation you describe is relatively rare: when coding you typically will be addressing blocks of text defined as functions; sharing an indent level ("ii" selects these); or otherwise selectable by vim in 2-3 keystrokes.

3. Even when that's not the case and the vim selection takes, say, 5 or 6 keystrokes, it has the advantage that your fingers never left the home row, so there is no wasted time "resetting."

4. Just as a tip: doing a "/" search for 2-3 characters after making your visual selection is typically enough to define your block, and will often be faster (and less of a cognitive distraction) than trying to eyeball or count the number of lines and doing a "10j" motion or similar.