Obviously if you are creating a new document, you may consider that you start from scratch in Pages, Numbers or Keynote. These apps are very powerful and have numerous features but many who have come from the PC Windows world are used to using the Microsoft Office products.
Personally, I considered myself the Excel and Word guru and found at first that I would gravitate to MS Office. This applied in particular to one complex spreadsheet that I was using which contained over 70,000 rows which of course Numbers does not support. Also, the complexity of the formulae made it difficult to convert. But, this was the only one and if I really needed this in the future, the free Open Office seemed to handle this very well.
Many of the difference require some different thinking. For example, Numbers does not support pivot tables but you can easily achieve the same result as pivot tables in other ways (let me know if you are wondering).
If you wish to check the differences, Apple have provided information concerning this on their site at https://www.apple.com/au/mac/pages/compatibility/. This also has all the documentation online as well.
MacMost also has very useful information about the products at https://macmost.com.
The main advantage as I see it for learning and using Pages, Numbers and Keynote is that they come free with every Mac and iOS device. MS Office costs money and for many people, the specific features in MS Office may be overkill, besides, Open Office, which is free, may meet the requirements such as my example where I have an enormous spreadsheet but then, if you are developing a spreadsheet, you may as well design it in such a way where it will work in Numbers.