Which day is more sacred or elevated, Shabbat or Yom Kippur?

Shalom u'vracha

Shabbat has uniqueness that Yom Kippur does not have, and Yom Kippur has uniqueness that Shabbat does not have. Shabbat is the joy of all days, and it is holier than Yom Kippur. In fact, violating Shabbat is considered more serious than violating Yom Kippur. One who violates Shabbat is punished by stoning if there are witnesses, whereas one who violates Yom Kippur, despite being liable for karet (a spiritual excision), does not face a death penalty by human hands. This is reflected in the Talmudic explanation regarding the reading from the Torah on our sacred days: on Rosh Chodesh (the new month) and during Chol Hamoed (intermediate days of the festivals), four people are called to the Torah; on holidays that are holier, five are called; on Yom Kippur, which is the holiest, six are called to the Torah; while on Shabbat, the holiest day, seven are called.

Additionally, one who desecrates Shabbat is considered a mumar (one who outright rejects mitzvot) for the entire Torah, whereas one who desecrates Yom Kippur is not seen as a mumar for the whole Torah, which affects several legal matters. On the other hand, Yom Kippur has its own uniqueness in the atonement it brings to the Jewish people; some say that Yom Kippur does not atone for those who desecrate it. On Yom Kippur, there is a revealed light from the upper worlds that is not present on Shabbat, and through this illumination, the Jewish people come closer to their supreme source.

Best wishes - Menashe Yisrael