I've had the misfortune of having to maintain and extend a new WP install now, where we used Umbraco before. Literally everything about Umbraco was better except for two things:
1) the requirement to run on Windows
2) the number of available plugins was smaller
The number of plugins thing is offset by the reality that Umbraco plugins were generally higher quality across the board.
What you gain, though, is a sensible way to create a content structure/ component blocks and templates that work in a standard MVC way with a data model and views. WordPress on the other hand... I want to cry every time I look at a WordPress template, even when using improvements over the core like Roots provides with Bedrock and Sage. It's all imperative functions that modify state, global vars and functions, exceptions to remove all sorts of random bundled scripts and an outdated version of jQuery, just barf-ola.
And that's not even getting into the fact that by default it runs basically everything on every single request unless you install a third party caching plugin. Good luck loading config values or whatever on "startup" because the concept doesn't exist. Umbraco had a much higher level of performance out of the box, and could use generally the same additional caching techniques and performance techniques if you want to.
I truly think these types of CMSes are on their way out, as they tie the presentation layer directly to content management. The future, to me, is looking like Headless CMSes linked to a static site generator like Gatsby or React Static.