Both services offer comparable encrypted protection for your files. Both Google Drive and OneDrive transmit the files to the cloud via HTTPS encryption, then encrypt your files using their own encryption keys.
This makes it much tougher for hackers to decrypt your data if they were able to hack into either service’s servers. However, this also makes it easier for both companies to read what’s in your files, or hand them over to law enforcement if they were forced to do so.