Inventory Scan: gpinventory vs Application Compatibility Toolkit

Hi there,
I'm searching for possibilities to do an inventory scan (aim is to make an
application consolidation) for a bigger number of PC's that are not all part
of a software distribution system.
So far I found the tool gpinventory and the application compatibility Toolkit.
Can anybody tell me which applications these tools will find on the client.
When I scanned my own PC with gpinventory I only found about half of the
application on my PC. Will gpinventory show me only applications installed by
an msi file?
Will the application compatibility Toolkit give me any more information by
scanning?

Thanks a lot for any information,
Tobias