Design Options in Area Plan
Area plan is a preferrable option for the General Arrangement Plan (GA Plan) as it can show the internal and external area, which could be tricky for Room. Area plan has the same feature as Floor Plan apart from the colour scheme for Area. Moreover, there is a minor drawback which the Area and Area Boundaries cannot be assigned to Design Option!
Therefore, if you want to have a series of design options to show different space options, then you need to create a new Area Scheme, which is quite tedious. Furthermore, you need to re-create the colour scheme to present different areas again! What a waste of time!
In order to overcome this issue, you need to get a help from Dynamo to automate the boring tasks.
[Dynamo Script to copy a colour scheme from one to another in Revit]
Main purpose of this workflow is to use Area Plan for GA if you need to show GFA or other area requirements that cannot be archived by Room.
Design Options in Area Plan Workflow
 Using Area
Create another Area Scheme for design option, and you can copy all the area and area boundaries from the original to new option. Then, you can transfer the colour scheme used for the original plan.
Better managing the design options
Easy to draw the boundaries
Area element can contain more information
Colour scheme must be re-created
Less intuitive workflow than filled region
Area boundary can be constraint to the wall, but it won’t be defined by the user. When creating the area plans, it will ask whether you want to create area boundaries from the existing walls. Therefore, it will be critical which one is constraint, and which one is not (manually updated).
 Using Filled Region
Create a filled region for design option. This workflow can be done in both floor plan and area plan. You can also tag the filled region to see the area and be copied to other views.
Faster and more intuitive workflow, but can be time-consuming depending on the scale or complexity of the project
Easy to copy and paste to other views
View-specific, which means all the works can be lost
Limited information available
There could be discrepancies of information that what it should be as it is done manually except for the area.
To Sum Up
It is important to note that the workflow should be flexible to meet the requirements such as limited time frame, the complexity of the design, and so on. I wouldn’t say which one is better, but preferably using Area would be better option if you can afford to using it (may require skilled team members as well).