I am actually leaning towards the registry query, even if it is little complex with all the sku options, it atleast works.
looking for a path that might not even be there since user can change the path during installation is utterly unreliable.

edit,
and what comes to the wmi query, does that not tricker the software inventory refresh?
you know, the one that spills 100 lines of event lines in the eventlog?
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