You can find a full breakdown of all valid values for font-weight in the CSS Fonts Module Level 3 Specification. Under section 3.2 (font-weight property) we find the following list:
- 100 – Thin
- 200 – Extra Light (Ultra Light)
- 300 – Light
- 400 – Normal
- 500 – Medium
- 600 – Semi Bold (Demi Bold)
- 700 – Bold
- 800 – Extra Bold (Ultra Bold)
- 900 – Black (Heavy)
You likely noticed that 700 is “bold”. So either way, you’ll get the same results. (The only other one which corresponds to a number is “normal” – 400.)
The complete list is:
normal – Same as ‘400’
bold – Same as ‘700’
bolder – Specifies a bolder weight than the inherited value
lighter – Specifies a lighter weight than the inherited value
There’s no real difference. It’s more about what you and your team are used to.