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Multicast is best suited for environments where you will deploy images to several or more computers simultaneously. If you are only deploying images to one or two computers at a time, opt for unicast instead.

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Cover of Exam Ref 70-695 Deploying Windows Devices and Enterprise Apps (MCSE)

Note

In an education environment, this most likely correlates to using multicast when imaging an entire lab and unicast for one-off imaging.