True BBQ takes time. The process cannot be rushed. Low and slow makes the meat tender by melting the connective tissue. You typically need to keep the temperature between 225-275. Gas grills have a hard time getting that low. Plus you can get a true smoke flavor with charcoal. Charcoal grills also can get hotter than gas which makes them better for steaks and the like where you want a good sear. That said, gas grills are convenient and much quicker to get up to temperature than charcoal which can take 20-30 minutes.