IBM i platform is best suited for transaction-based and data warehousing applications. IBM i has proved its high availability and continuity for core banking applications. Since IBM i provides a single server solution for the back end to the front end, it is a simple and efficient system for a business to bring up their application live.
I think for every business in the world Microsoft Windows is a good use as standard OS system. It’s easy to use and a lot of other company's use it which make it very appealing for user to learn more about Microsoft Windows. The Office 365 suite is really good as a free feature and used a lot by every user of Microsoft Windows. If you got a designer business I would recommend other brands that are specialized in that kind of work. I feel Windows will come short on that end.
It's easy to use, very straightforward, and user-friendly. It has improved over the years, but you still need to be careful not to shut it down improperly because that may lead to corruption and Windows being unable to boot. There is plenty of software available that covers most needs.
IBM i platform is single shop solution for multiple business requirements. Its database architecture and security options made it dependable among multiple business domain entities. IBM i is IBM's well-told and well-known system. IBM i is popular in companies in the manufacturing and supply chain business. Thanks to IBM that it kept IBM i (AS400) ever-evolving so far.
Microsoft Windows and macOS are both useful operating systems. There are businesses who much prefer macOS and some that prefer Windows. Businesses that revolve around industries such as game design, art design, graphic design may opt to use macOS due to its optimization with programs that revolve around these topics. Other businesses that are more focused towards Data or text processing may opt to use Windows due to its familiarity across the world and ease of access.