Hi Dev,
1). By creating the model attribute: we will use this option in case of the field is avaibla in stanadrd sap system. It might be in another under child context nodes and we will use BOL relations to access the attribute.
2). By creating the model node using the GENIL object and using its attributes in view: We will use this option incase of there is no standard provision to use. Means you want to create any custom assignment block with custom attributes then you can go for this option. More over we can use AET to create custom genil object. We have an option Create Table in AET.
3).Creating the field in Database structure using AET: We will use this option incase of there is no attribute in database relevant to your requirement then we will go for AET enhancement.
Hope this might give you little clarification..
Best Regards,
Dharmakasi.