Ooh, a grill thread....
Flavor; Too hard for me to compare because I grill using propane. I, nor anyone that I've cooked for has a problem with anything I cook using gas. Many moons ago, when I was a little guy, my father had a natural gas grill and my two uncles charcoal. They always rotated the family get-togethers and I don't recall anyone saying one cooking medium was better than the other. And I grew up to my old age of today pretty much around both, but most of used propane grills. I'm not even going to get into cooking over an open fire because that's a whole different animal.... camping, cooking over an open fire, or a fire pit in the backyard that's more about ambiance than it is flavor. IMO. And if I want a smokey taste, I can wrap up some chips in a foil packet and set them on a burner.
I think that grilling with gas it much safer than charcoal. If I didn't have my propane grill up on my porch, there's no way I would be playing around with charcoal at least 3x/week. Sparks, igniters... fun to play with, but lots of caution needed for sure on a wood deck. Gas is so safe that.... well, that it replaced wood stoves
Convenience? Who here that uses charcoal fires up the charcoal grill to grill a couple hot dogs for lunch, or burgers? Gas has charcoal for convenience (and being cleaner) hands down. If I light only two burners on my Ducane I have a 500+ grill in five minutes. All four and the flavor bars are cherry red and it's up to 600F. Like Joe C mentioned, very controllable temps, too. I even love my hot and cold spots for moving around food. Sometimes I'm not even grilling meat, I'll fire it up just to toss some potatoes on. Crispy skin, grill marks.... all in the matter of minutes.
I have nothing against charcoal grills, but I'll always own a gas grill. I do prefer the "days of old" though when they used briquettes and lava rocks over these "flavor bars".
Your mileage may vary