I've worked with several network device vendors in my 10+ years of being in the industry and my favorite continues to be Cisco IOS. Overall, Cisco IOS tends to be the most stable, the most intuitive, has the best TAC support, and has the best knowledge base articles and white papers.
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.
By this point, there are several "flavors" of the Cisco IOS such as XE, XR, and the standard Cisco IOS. While they are all fairly similar, there does exist syntax differences between them. It would be ideal if at some point in the future, Cisco is able to unify all of them into one standard operating system which would use the same syntax across all platforms.
While overall Cisco does a great job of QA'ing their IOS, no matter the release, there's always some minor bugs. I think it's important that Cisco continue to pour resources into their QA team to test their software.
While I'm very familiar with the graphical readouts of "show processes cpu history" I would love for Cisco to eventually find a more intuitive way to display this data. I can't begin to count how many times I've had to teach more entry level (and even mid level) engineers how this graph is interpreted.
I do wish that Cisco had something similar to Juniper's "commit check" or "commit confirmed". This helps validate the changes you're about to apply, and catch errors, so that you have a better idea of the impact of the change.
The data that Cisco IOS is able to provide is extremely relevant, it's fast, and it's intuitive. I also love that you're able to leverage things like macros or EEM scrips to run multiple commands at once. This is especially useful when you have more junior or entry level engineers in your environment and you want to provide them with a "shortcut" by having them type a single command to execute multiple commands.
We have found other Cisco software to be filled with added functionalities as compared to iOS. New NCS software has certain programmability features that are advantageous to legacy iOS software but are more complex to use for some users. Hence, we still have most areas of the network that functions using iOS software.
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.
