The main difference between the standard convection/conventional burner and the infrared burner is temperature. Infrared burners will get hotter and hotter much faster than standard burners and they way it heats is different. Infrared burners only take 2-3 minutes to heat up to between 1000-1500 degrees F near the burner surface, where the conventional burners take 10 minutes with the hood down to reach 700 degrees F near the burner surface and then lose a lot of heat when you open the hood to place food on the grill. This hotter temperature cooks food faster than the lower temperature conventional burners.
Infrared burners provide more direct heat that tends to go basically straight up over the burner, where the regular burners heat the air around the burner and that has to cook the food. As a result: infrared works best with the hood up, whereas the conventional burner needs the hood down to trap the warm air to cook.
Another result of this is that infrared grilling can be done in most weather conditions and temperatures since its method of cooking is not as reliant on heating air as other burners. Weather will not affect performance unless it is an extreme condition like very excessive winds or heavy rain. Temperatures do not matter as long as the liquid propane isn't frozen.
Infrared's direct heat tends to sear the meat or whatever you are cooking and create what is known as the Maillard reaction, which gives grilled food its good taste. Infrared also cooks food faster, so there is less time for the juices to evaporate, making food juicier when it is cooked over infrared burners. Conventional burners rely on heating air, so it takes longer to cook and as a result food tends to become dried out.