Interface Virtual-Templates are intended for dynamic access, in other words - dial-in and dial-out features from/to the router.
It is also use on PPP over Frame-Relay configurations as the command frame-relay interface-dlci xx ppp calls for a virtual-template to clone from, not a multilink interface. You can still use the multilink interface along with the virtual-template by binding the multilink with same ppp multilink group.
Another benefit of using a Virtual-Template that when the Virtual-Access is not in use, those resources are freed up by the router.
While, if you use Interface Multilink, those resources will be allocated permanently until you delete the interface from the config.
In terms of usability, they both offer the same kind of services and features under the logical interfaces.
All commands applied under the Interface Virtual-Template are valid under the Interface Multilink.