IBM AIX is a very powerful and extremely stable operating environment. It is well suited for applications that are business critical and cannot tolerate outages. It is best used to address large enterprise level application needs where stability and scalability are of paramount importance. IBM AIX is less useful for small enterprises.
Anyone with an iPhone or iPad would benefit from having a macOS-based computer. Additionally, the learning curve for a new user is much less steep than for a Windows computer. Apple has updated its OS for 20+ years, however, still maintains the same basic functionality (turn on/off, open/close apps, etc), the same cannot be said for Windows (Windows Vista, 8, 8.1, 11).
AIX is robust, helps the systems administrator, is built to prevent easily made mistakes. If you are used to other variants of Unix (in particularly Linux) there is no steep learning curve to get started with AIX. You need to learn the intricacies of the operating system, but that is true for any new operating system. AIX has built-in tools for almost anything you want and has the AIX Toolbox (on the web) for tools that are not included with AIX by default, but can be installed. Installation of AIX is modular, you can select with components and features you want to have installed. Installation of additional components (and usually also removal of installed components) is easy and straight-forward.
Compared to other Unix-like operating systems, IBM AIX is the one with a solid roadmap into the future and is likely to stay around for a long time (it is over 30 years old and still being updated with new features and components all the time). Compared to many Linux variants, the AIX operating system is more robust, easier to manage and well-supported by its vendor.
macOS just makes sense to me. Each OS has its pros and cons.. macOS works for me. It's well designed, intuitive, and efficient. But it's not cheap... well, macOS is basically free, but you need the hardware to run it, and the hardware isn't cheap. Pick the right tool for the job and for you. And even though macOS may not be thought of in an enterprise environment, it works remarkably well if configured properly. Tools like DEP and ABM from Apple enable device management and lock them to the company. Use an MDM like Jamf to push policies and packages. Jamf can also manage accounts and authentication. JumpCloud is another great product for account management. Although it might not be all included in the box, with the right knowledge, you can build a robust and versatile enterprise Mac infrastructure. You can even do zero-touch deployment in most cases with the correct setup. And Apple employs engineers to help you get it set up right.