Windwall is not objectively stronger than Unbreakable, they do different things. Besides, it is all relative to the kit. It seems you are trying to get in on the fuck Yasuo circlejerk.
Here's what you sound like:
Why is Morgana's q a better version of Ryze's q? It does more damage, and even roots, and has a longer range.
What's wrong with this statement is that Ryze's kit is vastly different, and a lot of the power of his q, comes from the interactions with his other abilities. Which are, reseting it's cooldown, amplifying its damage, and granting him a shield/MS.
Similarly, Braum's Unbreakable allows him to move around, which fits well with his ability to jump to and protect allies. You cannot do that with windwall.