If you consider performace as speed, then yes. Mendix always retrieves all columns of an object so the more columns you have, the more data it will retrieve. And slower it will get, and possibly run out of memory in the process of retrieving all that data. And in most cases you don't need all the attributes. So you should consider a domain model with associated entities and attributes where you retrieve the information that you need for your actions.
Hi Ben,
It must always be a balance and the decision must be based on the business requirement and performance requirement.
Hope this explanation helps.
- Nirmal