The most secure method is getting a cloud or dedicated server through a reliable company (I would recommend ServerBeach as I've used them for over 10 years and have great Value servers for your file sharing). Then, have an FTP account or a cheap copy of a file sharing system script and make your own service-- specifically for you.
I don't want to cloud my personal photos to Google. Who knows, they already have image recognition technology. What if there's a picture of me hiking or drinking a Coke? Will I be targeted for hiking boots and Coca-Cola?
I know my server is secure, it's backed up locally on a 2nd hard drive in case the 1st fails and also in another remote location. I've lost 6 months of my baby's life from a corrupt MicroSD card and it's not going to happen again. Now I use FolderSync ($2.99 Android app) to backup every picture I take automatically via FTP.