Well, if you travel at a certain time of year every year than there are some advantages to a certain UY.
Let's say you travel every April school vacation. You wouldn't really want a UY just after that vacation - since your reservation will lock up lots of points and if something happens where you cannot go, you only have until the UY anniversary to use the points.
Let's imagine you vacation in April. UY is June. You have to delay the April vacation last minute - you'd only be able to rebook or rent points into June. The banking window has passed and the reservation was a final transaction. Now, let's say you have a December UY, just think of the expanded window you have have to re-book.
Now same example - if you have June UY you need to bank in January. If you have vacations booked you're okay but if you're undecided about a typical end-of-year vacation and you have to bank.....you have to bank.
This is my understanding of why you want a certain UY. Honestly, I borrow as much as possible so it never really affects me.