When propane combusts, the chemical reaction produces water vapor which makes the meat mushy when smoke roasting foods. If you're using a direct heat method (like with burgers) then it's not as bad, but you're not really getting the smokey taste which is the entire point of grilling. If you're using a direct heat method though, you still want charcoal because it burns hotter than your standard gas grill which produces that nice char to seal in the juices of your meats. The gas grill has one advantage: it's faster. If that's your motivation, then just make it even faster by staying in the kitchen. Gas grillers probably use the microwave to cook, too...
I use everything at my disposal, chief. Charcoal freaks are free to practice their strange rituals with many potions and rattles and much chanting of haughty incantations. I find them an fascinating people . . .
I'm not sure how they cook with "potions and rattles and much chanting of haughty incantations", but I use a wood fire and it takes about five minutes longer to light than clicking the gas grill and tastes 100 times better. Not everyone appreciates skill, shich is why McDonald's is so popular...
I have both, but for simplicity I am finding myself using gas more and more for steaks. I have taken to marinating steaks for 3-4 hours then applying a dry rub about 30-45 minutes before cooking. I find setting the temp at 325 degrees using two burners works great. An inch thick steak takes about 17-18 minutes per side to get to a medium-medium rare on my grill. The steaks just fall apart and are absolutely succulent. I have been using the original version of this for steaks: Daddy Hinkle's Instant Meat Marinades And Seasonings -- For Cooking Steak, Chicken, and More! For chicken I still love: Butler's Gourmet Foods
I use charcoal almost exclusively. nothing against gas grills. I'm just a poor boy from down the bayou, so I just use by $30 charcoal pit. but I don't cook on the pit anywhere near as often as I did in the past, so throwing down the extra money on a good gas grill isn't something that's really justified for me.