He specifically said he said he would be switching from Dropbox, and the privacy question isn't whether or not someone could hack Drive, but rather can he trust Google to not examine his files to better characterize him for targeted ads. Regardless of whether Drive or Dropbox is more secure from hackers or the NSA or whomever, Drive's business reason for existing is specifically so they can look at your files, whereas Dropbox's business reason for existing is so that you can give them money to store your stuff. Google can make these kinds of price cuts because the money people pay them for it is only a portion of the income they receive as a result of Drive.

I say that as someone who uses Drive instead of Dropbox because the balance of their respective pros and cons, for me personally, leans towards Drive. I've got no emotional attachment or aversion to either one.