Some of the most popular cloud services for personal and small business storage are DropBox, iCloud, OneDrive and GoogleDrive.
They all work in similar ways (storage outside of your own computer/device/network) which can be synchronized for convenience (you don’t have to download/upload – just put the files in the synced folder on your device and they’re automatically copied to your cloud storage).
All of them have a Free level of storage: OneDrive – 5GB attached to an Outlook.com or Xbox Live account; GoogleDrive – 15GB for every Gmail account; iCloud – 5GB with each Apple account (usually when you have an Apple device); Dropbox – 5GB with a free account.
Dropbox isn’t integrated with an email provider (storage is all they do) but can be integrated with either Office 365 (Exchange hosted by MS/Outlook web or local client) or Gmail. This can create a useful division of file storage – keeping main file storage in OneDrive/Sharepoint and sharing externally through GoogleDrive or Dropbox.
There are some differences in function, and depending on what else you’re using, one may be easier or more difficult to integrate. OneDrive makes it a bit more complicated to share files and folders outside of your organization — assuming you’re using it as part of an Office365 business; Google Drive is probably indexing your files to send you ads, iCloud is so entwined with your Apple devices that it’s really hard to get out of.
With all of them, you have to be aware of the synchronization – it’s easy to add a file to your synched folder and have a copy available from anywhere, but that also means that if you delete that folder, you are probably also deleting it from your cloud storage.
If you’re using a local client to sync files, it may also be vulnerable to any attacks on your computer (e.g. viruses or ransomware could be able to attack any drives mapped to your device).
Backups and archives are still necessary — while automated backups are easier, it’s more secure to backup then disconnect and store your backup media separately.