Is it better for the worshipper, after the Isha Sunnah prayer, to intend Witr for all the rakahs, or to intend Tahajjud/Qiyam al-Layl for some of them and Witr for others?

Scholars have differed on the appellation of Witr: is it the single rak'ah, or the sum of the rak'ahs prayed before it and concluded with that single rak'ah? This leads to their differing on the intention for the rak'ahs preceding Witr. Some scholars hold that Witr is only the last rak'ah, while others believe it is the totality of the night prayer concluded with the odd rak'ah. Witr is part of Qiyam al-Layl (night vigil prayer), and there is no contradiction between the intention for Qiyam al-Layl and the intention for Witr, as it is also Tahajjud. Some scholars maintain that Witr is the name for the separate rak'ah, or the connected five or seven rak'ahs, whereas the even-numbered rak'ahs preceding it are not called Witr, but rather Qiyam al-Layl or Tahajjud. It is sunnah for Witr to be the last prayer of the night, so that one's deeds conclude with the best.