Dec or April UY would work well. What I would think about is the secondary times you might want to go.
Dec UY works well for travel from December through August. It leaves fall as the most vulnerable. April UY would work well from August through December, leaving the winter the most vulnerable.
Since you are going resale, you would also purchase Oct UY and that would cover both Dec and May travel.
As mentioned, your UY doesn't impact when you book, but if you know you are traveling certain times, having one that allows the trip to be in the banking window does give you more flexibility in terms what to do.
Good luck!