Let's start saying that even though Google Drive is cheaper than Dropbox, Google Drive is 25% of Dropbox cost. But the big issue for me is the crossplatform support.
I use Linux a lot, and I also use a Blackberry, and both platforms are only supported by Dropbox and not by Google Drive, so at least for me I prefer Dropbox.
I have a Google Apps Premier account, and I can use my Google Drive, and I may use it as an extra backup of some important files (maybe encrypted, so Google can't scan them). But I'll stick to Dropbox as my main synchronization and storage tool in the cloud.
Now, if you use Google Docs a lot, or if you have a Chromebook you may have to go with Google Drive. It offers a really nice integration with Google Documents.
In my case I prefer to use Libre Office to edit my documents, Of which I have a copy in both my Linux and Mac computers.
Your needs may be different than mine, so before to decide which one of them is for you, read, study and test them both.