I use and enjoy Google products including Gmail, Google Drive, Blogger, Google Maps, Search and Google+. I trust Google and marvel at what the company has accomplished.
Google Drive offers features that Dropbox does not -- like Google Docs and full text search even of PDF documents. In addition, Google Drive storage is less expensive than Dropbox.
But in using Google Drive for about a year I find that the Google Drive app for the Mac sometimes does not sync all files. I get an error message that certain files did not sync. If I quit the Google Drive app and restart that usually resolves the issue. Over the last few days when using Google Docs the cursor has been skipping around and I really can't control it properly with my trackpad or mouse. Finally, sometimes when I use Google Drive at the Google Drive website in Chrome I get an error message and none of the files in that folder appear. Later they reappear. But it is unsettling.
I have never had reliability issues with Dropbox, which of course lacks an equivalent to Google Docs. But everything just syncs. I have not had a problem with Dropbox in over two years. So I am inclined to stick with Dropbox for my cloud storage even though Dropbox costs more and offers fewer features. Reliability is my top priority. I keep all my documents either in Google Drive or Dropbox or both. I don't have a large volume of documents and like having them in the cloud so if I get a new computer they will just be there.
I hope Google focuses more on Google Drive's reliability. To me, this is way more important than adding features.