Gas fans say anything charcoal can do, gas can do better. The magic comes from the drippings—when it hits the heat, it turns into smoke and coats the food in that delicious flavor you can only find by grilling. Charcoal has nothing to do with that. If that's the case, why bother with the grueling task of getting charcoal going and waiting until it reaches the right temperature? All that time would be much better spent putting meat on the table.
Purists say the only way to grill is with charcoal. Otherwise, what's the point? If you grill with gas, you might as well just cook with your stove. It's just not grilling that way. The charcoal itself is what matters—it adds a smokiness that's unique to charcoal. Gas has no distinct taste or smell and that's probably a good thing. But grilling is special. It's something you shouldn't cut corners with.