Circumstancing : If we want to some change in the rule based on time or Property .
Example: We have to make some change to the flow which is already in prod and new change should not effect the existing cases in prod.So in this scenario we can use Circumstancing based on time so based on the the time it will pick the new flow for new cases and old flow for old cases.
Based on some dropdown value we can to display the respected sections. So in this scenario we will create the section with circumstanced property
Decision Table : Based on the different Params if we want to set the response Value .
For example If Gold Rate is 30 And Category A Then Display ABC Value
If Gold Rate is 30 and Category B then dislay BCA Value
Based on different conditions if we want to display the response based of if else conditions then we can go for decision table.