If you only have a small number of users to migrate to Office 365 from your Exchange 2010 or higher organization you might not be enthusiastic about the various options available to migrate and the number of different tools you need to master to set up and migrate using Exchange Hybrid functionality.
The Express Migration option allows you to avoid getting your hands dirty. A typical Exchange Online migration, even for a small migration requires a choice. Do you want automatic client reconfiguration, offline caches being retained and a password synchronization, or do you want to provide users new passwords and reconfigure every single client? In the past, if you wanted a high-fidelity migration with those benefits, you needed to understand how to set up Azure AD Connect, understand how to up a full Exchange Hybrid, and learn about the Exchange Admin Center functionality for managing mailbox migrations.
Instead, the Express Migration option automates the setup of these components for you and provides you a single migration dashboard within the main Office 365 portal, allowing you to concentrate on getting people using Office 365 rather than learning about how to perform a Hybrid migration just the once, and allows you to use the great benefits of Hybrid, like automatic client reconfiguration, offline caches being retained and a one-time password synchronization – all of which are not possible using the alternative cutover migration approach.