I have only ever had a real problem with the Crocodoc formatting. Once I download the file the formatting seems to be as intended. In my business class formatting is important, and I download anything that doesn't look right before I grade it just to be sure.
When the formatting's a problem with the download it's usually because I'm grading on a computer running a different version of Office than what the student used to submit the file. I can't really blame that on Canvas, though.
I have had both. It seemed to stem from students using an older version of Word, or using software other than Word (Open Office, or Pages) and saving their document as a .doc
I tended to only notice the issues when students had highly formatted documents, like equations or tables.
Never found a solution for the older software issue. I started using Google Docs and had students submit URLs. If you can get past the potential "cheating" issues with late alterations, it may work better.