Infinity, not because arrows are hard to get (even quite early), but because it's easier to watch the durability bar on an Infinity bow than keep track of arrows in inventory.
I do have occsaional use for Mending bows: one simple example id to start the aggro chain in a gold farm:
there is planety of Xp to be had (bow kills often do not allow easy recovery of the orbs),
a Mending / Unbreaking 3 / Power _0_ bow removes the chance of single shotting the target ,
arrows stack to 64 (while eggs and snowballs stack to 16) which decreases the number of atacks of ammo one must transport
The same reasoning applies to Ghast tear farms as one can attract and remove zombie pigmen with the Mending Bow but use a normal hunting bow on the Ghasts (usually single shot).
