Well, they all have their reasons for existing.
For the most part I use Pages. I'm very familiar with it, it's got good collaboration features and support LaTeX for maths. Now for some things I will just do LaTeX, but Pages is quicker to set up how I want in most cases. Now when I say it's got good collaboration features that's because my study partner is also on a Mac, so all our databases reports were written in Pages with LaTeX for equations. But for working with Windows users I haven't really found a perfect system yet. Pages on iCloud just isn't really as nice to work with.
I realise it's very feature rich and influential, but as far as I'm concerned, Word can go and do something I shouldn't write here. Just absolutely hate it.
For Linux I like Libre office the most. Open is slower to develop, probably more stable though, and more like Word, but perhaps exactly because of that I prefer Libre. Though it's also way too much like MS Office for my taste.
I don't touch Windows btw.
For doing screenplays I've used Scrivener in the past but moved over to CeltX, which is a dedicated screenplay/script writer. And it's really good for it. I've also had good results with a custom template for Pages with Courier Prime downloaded as the font, but CeltX looks just as good with pre-configured short cuts just for scripts.
For LaTeX co-operation I can highly recommend Overleaf, formerly shareLaTeX. It's the Google Drive of LaTeX. For local work, TeXMaker is nice.