Persistent disks can be backed up using either images or snapshots; the two services seem similar but differ in some subtle ways, so let's be sure we understand the differences:

• Snapshots are best for data backups, they are cheaper, and incremental snapshots are possible too.
• Images are best for infrastructure re-use, such as exporting a VM image for use in a different project or as the basis for a Managed Instance Group.
• As we just mentioned previously, only images can be used as the basis for an instance template, which in turn is used to create Managed Instance Groups. Snapshots can't be used for this purpose.
• Images can be shared across projects and assigned versions and organized into families, marked with metadata, such as deprecated and obsolete.
• A fresh VM can be spun up using either a snapshot or an image, but with one difference: an image can directly be imported into a VM, whereas a snapshot will need to first instantiated into a persistent disk, and that persistent disk can then be used to spin up the VM.
• Snapshots are global, whereas persistent disks are zonal; so, if you'd like to move a persistent disk from one region to another, snapshots are the way to go.
• Neither images nor snapshots will work with local SSDs; they both only work with local or persistent disks.