Choosing between MS Word, PDF, and latex formats when submitting a manuscript for publication when all are allowed? I've been working on an article, and for ease of collaboration among co-authors and advisers I have used Google Docs thus far, so I'll likely need to do at least a little post-formatting once in .doc format. In addition, I use linux and LibreOffice when I have to, and I generally dislike using MS products.

I'm now preparing the article to submit and the journal I am considering accepts a wide range of file formats: .doc, .docx, .rtf, &amp; .pdf (with .tex files after acceptance).

I feel inclined to put things in LaTeX since I am well-versed and like the idea of having finer control of the appearance of things, but it will certainly take a bit more time and I am ignorant of the layout process journals use when preparing an article.

Is there any real benefit of using LaTeX or another format when submitting an article to a journal (in this case PLOS One)?
That all depends on the journal you're submitting to. Quite some journals that accept Latex, also provide a template to use. With a template available and knowledge of Latex, it should be fairly easy to convert the GoogleDoc to Latex if you download as HTML and then use eg Pandoc to convert to Latex (explained here). 

But people who are not comfortable with Latex, are likely better of using another option. Converting from GoogleDocs to .doc or .docx generally also requires an in-between step using PDF, and will generally give some layout issues, but when a paper is bound to be submitted it's not really the time to learn Latex.