What is the ruling on reciting another surah instead of Al-Ikhlas in the Witr prayer?

The Sunnah for Witr prayer is to recite Surat Al-Ikhlas, or Al-Ikhlas along with Al-Mu'awwidhatain (Surat Al-Falaq and Surat An-Nas), as the Prophet, peace and blessings be upon him, did. However, if someone has not memorized them, or if they have a set portion of the Quran they regularly recite, they may perform Witr with whatever is easy for them. Their Witr is valid, even though they have forgone the more preferable option.