Or four well placed arrows. Nobody alive can shrug off an arrow in the eye.
Yeah, but in D&D terms, the "arrow to the eye" requires a crit or a rogue or someone with the sharpshooter feat. Or opponents with very few hit points.
The point is that guns (in theory) do comparable (or greater!) damage without requiring anything more than proficiency. (Again, this if you are wanting to implement 'realistic' gun damage - if you are doing Hollywood guns, then they do just as much as a longbow or heavy crossbow.)
Guns are both easier to use and do much more damage. If you are being realistic.