Before selecting a writing platform, consider the following questions concerning the document structure and content of your writing. One or more of these considerations may settle the issue for you about what platform to use.

Is there a writing template available for use with the platform?

Templates can save considerable time that you can devote to writing rather than structuring documents. Templates may be provided from within the software. Also look for externally available ones.  For example, does the graduate school provide a template for writing a dissertation or thesis? If you are submitting a manuscript for publication, does a journal or book publisher provide a template? Is your chosen "writing platform" compatible with that template?

What is your "document type"?

Is your document a dissertation or thesis, a technical report, a journal article, a book, or a preprint?  Using your chosen platform, how easy is to format a document in one of these formats?

For example, dissertations, theses, and books require chapters (in addition to sections), which are typically lengthier than the sections that characterize journal article and preprints. Also, how can create an outline structure, supply headers, and navigate between sections and reposition them? What capabilities do you need to anchor specific items such as figures, equations, or tables, and cross-reference them within a document?

Again, it is important to search for templates for a project as large as a thesis/dissertation or a book, for which chapter structure is critical. This will save you from having to spend lots of time formatting a document on your own!

Are you collaborating with someone?

This may limit the tools you can use, if you want to save time exporting to, or reformatting your document for, the different platform of a collaborators.. Also, consider whatever citation management software your collaborator uses. 

Does the collaborator need the ability to work concurrently on a document or just work on it intermittently at leisure?. For the latter, it may suffice that the platform's "exporting/importing" capabilities enables one author to export a document for import by a collaborator using a different platform. In other words, how interoperable is your platform with that of your collaborator?

Exporting/importing capabilities have two flavors. One is what the software can do automatically. The other is what one can do by cutting and pasting content into, or out of, the platform. We're focusing just on automatic capabilities in below comparisons.

Also, what commenting and comment-tracking capabilities does the platform have?

Are you submitting a paper for publication or a thesis or dissertation?

If you submit your work for publication, also consider the publications file type and formatting preferences. See if they provide a writing template. If you are working on a dissertation or thesis, check guidelines or templates provided by college and department.

What type of document are you creating?

Is it an article, book, technical report, or thesis/dissertation?

 What are your content types?

 Equations, tables, or figures?

Does your writing have special feature?

For example does your writing require a type of font, and what is the best font for the distribution (e.g., pdf versus paper)? Will it incorporate special characters?  

How might the platform facilitate your note-taking procedures?

See the notes in the page below about this topic, and note-taking considerations more generally.