If equipment has its own metadata, then I'd use an association (a child association should be fine).
Its easier - you can use the Alfresco APis to manipulate equipment (no need for custom serialisation into a single prop) and you can use the dictionary to provide any additional meta-data for your equipment properties.
You can still search on all these attributes. In fact, you'll have better control over search if you have a seperate node for equipment with its own set of properties.
I'm not sure there's noticable performance differences with either approach.