I will throw my 2 cents. Overage is usually a better deal but not always. If you are getting a day or two of overage but your sub trip is a long trip you might be better off accepting sub. First of all, if you are coming from an international trip you have a 48 hours duty free buffer in which scheduling can not assign you a trip. This buffer will be in the initial sub window, meaning they can not assign you a trip in the initial sub window. You get paid for 3 days right off the bat, they go into daily sub windows.
Do the math and see how much overage you will be paid and compare it to the sub trip. Obviously if your trip got extended 4 to 5 days overage is the way to go.