Upgrade/Migrate 4.1 to 5.1

My current enviroment:

2 ESXi 4.1 with vSphere Essentials.  One VM is running vCenter.

I have just purchased a new server as a third host and want to upgrade my enviroment to 5.1, keeping the vCenter duties on one of the original hosts.

With 5.1 having an appliance available, is there a path to migrate from a 4.1 VM to the 5.1 appliance?  Is there any advantage gained by using the appliance, rather than just upgrading the 4.1 VM to 5.1?

All hardware, software and licensing requirements are met, so this is a question of best practices and path options.

Thanks!