[azinman2]

My experience is that file sync is all about edge cases, and there are so, so many. I believe Dropbox is the only one that has solved most of them (a function of time, energy, and large user base).

A colleague just had google drive not properly syncing for 2 weeks, and all of the sudden it started working except it overwrote a very active Sketch file with the two week old copy (and no duplicate "conflict" copy made as Dropbox does). Google around and you'll find many such stories across all services.