From the Learningpath Master modeling Microflows:
List Functions vs. Loops
In general, list functions (aggregation/operations) are used when you want to apply logic to a list as a whole. Loops are used when you want to apply logic to each individual object in a list.
However, you may encounter situations in which using a loop would provide the same functionality as using a list operation. In these cases, it is important to evaluate if it is possible to use a more efficient list function instead.
Objects in Memory
When you are dealing with objects from the database in your microflows, you will mostly be using XPath to perform actions such as constraining, filtering, and sorting the data. However, you cannot use XPath for objects that only exist in memory.
That’s where List Operations come in. They are used when you are working with lists that only exist in memory and not (yet) in the database (for example, when you are working with non-persistent objects or persistent objects that have not yet been committed). These are some typical scenarios in which this is the case: