A double cab will have a seat behind the driver. An extended cab is just that, an extended cab with space behind the driver, but no seat. Usually not as large as a double cab.
This spring my wife and I would like to go on a trip, pulling our travel trailer. We may be taking or teenage son. A crew cab may be out of my price range. Over time extended cabs have gone from barely holding grocery bags to full seating. What year gm, ford, or dodge full size will...