Do smokeless grills have an advantage over gas grills?
Flavors don't develop by dripping onto the heat source

Flavor can enter a meat from smoke, but you want the flavor of hardwoods like hickory or apple. You do not want the flavor of burnt grease; I have never heard anyone describe burnt grease as a pleasant smell or taste. 

Therefore, you want the drippings to go somewhere that isn't the heat source. For some fatty foods this can be a problem, particularly 70/30 hamburgers or a pork shoulder. Many barbeque-ers will put a drip pan (a small tin-foil pan) into their grill to catch grease, keeping it away from the coals or the gas flame. Also, the drippings from some cooked meats can be re-used (like in a gravy), another reason for a drip pan.

I have never seen or used a smokeless charcoal grill. But, as long as the device works as promised and keeps the grease away from the flame, there should be no change in flavor of your finished foods.