IMHO it is (1) a function of the other entities with whom you are exchanging files/information and (2) your budget.
A perfect version of MS Office for the Mac has yet to be written. Office 2016 has some bugs that were nonexistent in Office 2011. Seemingly simple things such as fonts, bullets, numbering or page breaks can pose minor to major issues when exchanging files with Windows only Office users. This has been the case for 30 years.
As Allan Eckert wrote, the cheapest solution is LibreOffice. If you primarily exchange files with Windows only Office users, go with MS 2016 or the 365 subscription, and hope some of the bugs will be addressed in future releases. Remember that you can always try LibreOffice first and go with MS Office if you have to have it.