Indeed, I am using both Alteryx and Power Bi in my daily job. Alteryx is a great tool and very different to Power Bi. You can’t really compare the two.
Most companies who were using Alteryx were using Tableau as well, as there was no really data prep solution inside Tableau (before they created Tableau prep which is highly inspired by Alteryx).
You can do a lot of things inside Alteryx, you can visually see the steps you do, it is code free and code friendly, you can integrate R, Python, do geospatial analysis. You learn how to use it quite fast, so it can add value to your company from the first month of use.
It is easy to use for business people and a great tool for the citizen data scientist. The main disadvantage of this tool though is the pricing and the scaling.
For me, Power Bi and all Microsoft Ecosystem is doing 95% of the job.
I do have use cases where I use Alteryx, but I use it mostly for data exploration and algorithm prototyping before we integrate in central ecosystems like SQL, Synaps, AS etc.
If you just get started with your Bi environment, you do not have a lot of IT resources or support, Alteryx can be a solution in addition to PBI.