Charcoal. Not as easy or convenient, but the flavor is far superior to gas. In the summer I barbecue almost every night though so I use a gas grill a lot as well. However, my gas grill has a dish inside of it for woodchips. I have a shitload of cherrywood chips and throw a bunch of them in when I bbq any sort of red meat. I use a blowtorch to get 'em going, then just let the gas do the rest.
I use one of those chimney things when I bbq with coals so that speeds the process up and I don't have to use those bullshit coals from Kingsford that are covered in lighter fluid. I also use the wood chips when I use coals; I just keep them on the outer edges of the coal pile to add some flavor. Of course, then there's the coals that have the little chunks of hickory already in them. You can get a bag of them for about $5 from Trader Joe's.