To be clear when I talk about wills, I'm not saying to do away with partition entirely, just to give the player at least some control over it.
As example; in one game I held the kingdoms of Nicaea, Anatolia, Syria, and Jerusalem. Nicea is the primary title and they were acquired and listed in the order I put up. My king had 2 sons for most of his life. Now, these kingdoms are in a line, rather than blobbed up together. If we ignore the religious significance of holding Jerusalem for a moment, it would make more sense to break the kingdoms up regionally, giving one son Nicaea and Anatolia, and the other Syria and Jerusalem. However, Partition just goes down the line and hands things out: Son 1 gets Nicaea, Son 2 gets Anatolia, 1 gets Syria, 2 gets Jerusalem. instead of either son having a solid territory to control, each of them has a split territory and I could do nothing about that. Now, having split territory is not unreasonable or uncommon in this time, but even the way it was distributed made no sense. Jerusalem is a hugely significant prize in christendom, which should give it much more weight than just going down the line. In fact, just before his death, the king had a 3rd son, who was suddenly in line to inherit Jerusalem. My eldest son got Nicaea and Syria, the middle son got Anatolia, and the youngest got Jerusalem.
Why? Why can't I have any control over who gets what?
In this situation does it not make more sense to give the eldest the primary title and Jerusalem, the two biggest prizes, the 2nd eldest Syria, still significant, but less stable and in need of an adult ruler (It had been mostly converted to orthodox but not completely and the culture was still giving issues), and the infant gets Anatolia, stable and culturally neutral if I must give him anything.
I've said this before in another thread: Let me create weird succession issues. Let me favor a dutiful and virtuous second son over a shitty eldest son. Let me give an infant massive amounts of titles and piss off his elder siblings. Let me write a newborn or very young child out of a will so he doesn't get assassinated by his older siblings. Wills open up so many interesting possibilities while not throwing partition out the window.