What is the difference between regular Sunnah prayers (Sunan al-Rawatib) and emphasized Sunnah prayers (Sunan al-Mu'akkadah)?

The Sunnah Ratibah (regular Sunnah) is the Sunnah that follows another [act of worship], and it is sometimes applied to the temporary, non-obligatory prayers. It is considered Mustahabb (recommended) by the majority of jurists, and the Hanbalis consider abandoning it Makrooh (disliked).

As for the Sunnah Mu’akkadah (emphasized Sunnah), it is what the Prophet, peace and blessings be upon him, consistently performed and never abandoned. The Hanafis call it "Sunan al-Huda" (Sunan of Guidance). The one who performs it is rewarded, and the one who abandons it is not punished, but is blamed and reproached.

The Sunnah can be both Ratibah and Mu’akkadah at the same time, such as the pre- and post-Fard prayers, which are ten rak'ahs as stated in the hadith of Ibn 'Umar. It can also be Ratibah and not Mu’akkadah, such as the four rak'ahs before the Asr prayer.