One caveat about Google Drive is that if you use Gmail, Google Photos, or other Google products, you could very easily burn through those 15 GB before you know it.

However, you can get an extra 500 MB of storage space for every friend you refer to Dropbox, for a maximum of 16 GB of free storage space. Google Drive offers 15 GB of free storage, while Dropbox only gives you 2 GB. If your primary use for Google Drive or Dropbox is free storage, Google Drive is the clear winner. However, Google Drive’s syncing methods leave your documents more exposed while in transit, as each document must be entirely encrypted before being stored, rather than in sections like Dropbox. National Security Agency has approved this encryption standard to protect information that has been classified top secret. Both use strong encryption to keep your files safe when they’re being stored - Advanced Encryption Standard (AES) 256-bit encryption. Google Drive and Dropbox offer two-factor authentication and encrypt your data when in transit - from the cloud storage service to your device, and vice versa. You can collect photos, videos, and other file uploads via custom online forms and send them to Dropbox or Google Drive automatically with Jotform! Security

How to transfer google drive to dropbox