Along the lines of what MrHoffman wrote:
I think this now becomes more based on which software does one want to use. We have Word v. Pages v. LibreOffice/OpenOffice etc. Most will open files and save to other formats but the degree of interchangeability is limited when you start using more advanced functions. You can also take under consideration how robust you want your applications to be and your technology environment in general. If you're needing this for a place where everybody is swapping files between Office then you pretty much need to go with Office. If you're in the habit of keeping Macs until they die completely then using applications that need constant updating and will only work on a narrow range of machines may not be the best. Apple works on a 5 year moving window (maybe stretch it to 8) with you buying new equipment every 5 years or so so you can always be running the latest operating system or at least one that's only a step or two away from the newest. You also always have to make sure you archive copies of software because things they have up for download today may disappear tomorrow.
Me, I use TextEdit or BBedit for 98% of what I do. Basic text styles are likely to have the greatest degree of permanence. If Ineed to make things "pretty" I'll then copy and paste my archival text file to something (I use LibreOffice because new versions still work on Mavericks OS) else and beautify it there. I still keep things in a text file because that's most of the work and I suspect I will still be able to open it 30 years from now.
