While I totally trust Google Drive with all my files and sensitive documents, I prefer Dropbox when it comes to the syncing option. Moreover, you can check out a head-on comparison of Google Drive VS Dropbox to get a more clear idea of what are you dealing with and aspects on which you are missing out. I am a Dropbox user and I have never faced any issues with it. Although where big companies like Apple do have issues with their online cloud storage services, I am really satisfied with what I have. Peace.