The Mishnah Berurah (90:28) quotes a teshuvos Radvaz, who discusses a prisoner who was permitted to daven one day with a minyan. The question is which day he should choose. Should he request to go to shul on Yom Kippur or Purim?
In the end, the Radvaz rules that he should go to shul at the first possible opportunity because if he pushes off the offer, you never know what will be. But we can see from this the importance of these two days: Purim and Yom Kippur. He didn’t even write Rosh Hashanah. Purim and Yom Kippur are at the top of the list of days to take advantage of davening in shul.
Don’t miss the opportunity! Plan the day around tefilah!