If you control it so the floor temp below the substrate is of right temperature, when the frog burrows down it will get heated up and then if it wants to cool down it will move an area away from the heat mat. Because the substrate is kept moist the heat will rise to some degree. In my opinion heat lamps are better but not for the same reasons as a lot of people. Heat mats don't warm the entire enclosure but just where the mat is situated. With lamps you get that hot spot and then also a little ambient warmth and this is best rather than the frog being hot and cold. However of room temp is not too cold then heat mats would be fine. It's very important to use a high quality heat mat aswell as thermostat and make sure there's airflow under the tank to prevent it from overheating and failing which could cause a fire