Two juristic texts use Sunnah and Mustahabb sometimes closely and sometimes with a distinction. What is the correct approach?

Sunnah and Mustahabb

• Always treat them as exactly the same technical term.
• Consider the juristic context and technical usage; because the rulings and degrees of Sunnah have further detail, the two terms are not necessarily identical everywhere.
• Ignore context and decide the meaning only from the order of the words.