Dash
- Dashes are recommended by Google over underscores (source).
- Dashes are more familiar to the end user.
- Dashes are easier to write on a standard keyboard (no need to Shift).
- Dashes don't hide behind underlines.
- Dashes feel more native in the context of URLs as they are allowed in domain names.
Underscore
Underscored_text is selectable as a whole by double clicking in some devices and long-pressing on mobiles, whereas with dash-separated-text the same actions select each
separated wordl --Titus