What does a pencil have over a mechanical pencil? Mechanical pencils never need sharpening, infinite supply of lead of various type and and they seem more environmentally friendly (assuming you keep using the same for many years).
2mm mechanical pencils are more versatile that way, but also generally heavier, unless it's something like a Faber-Castell TK9400 or Kitaboshi Otona no Enpitsu.