I am using the ECK module to build custom entities. When using custom entities, the decision must always be made: shall I create a number of entity types or shall I create one entity type with a number of bundles.
From a usability perspective, the latter is obvious since, just as the node system, all entity types can easily be connected in views. It gets harder when different entity types must be used in views.
Apart from that, I assume that there must be a benefit from using multiple entity types. It has something to do with memory that drupal carries around, but it is not clear to me what exactly makes a difference.
I am aware of the benefit of using entity properties instead of fields. However, most of my entities use fields that cannot be replaced by a property.
So the question is: should I in general aim for using more entity types (each of which automatically create one bundle) or should I not worry about performance impact and create all bundles under one (generic) entity type.