AL is only for VMware environments, while MP is ment for other Hypervisors as well.
AL does not require the installation of a McAfee agent, but requires the VMware thin agent (part of the VMware tools) to be installed and enabled.
For large VMware implementations, the usage of AL is preferred, as it integrates better with VMware.
Move is preferred above VSE, as Move can scan files and cache results for multiple servers, therefore avoiding scanning the same file (like OS files) for each server over and over again.
As file transfers are kept within a host, this is not really a performance issue.
Is this true for AL (SVA) or for MP (Offload Scan Server) too? So in case of MP/OSS - would you deploy one OSS per Host? I thought one per cluster would be enough.
Ideally you do have 1 scan server per host. However, there is no real need for that for MP. Whenever your environment and network can handle the offload scan file transfer, you can use 1 per cluster.