Neither!?!
actually if im only doing 1-2 whole briskets I trim almost all the fat off, maybe leaving 1/8" - 1/4" on it. Where ever there is heavy fat I will hack it out put on the rub use a waterpan and when I add fuel I will also spray with whatever concoction I choose. My therory which seems to work, fat will only melt off so much, therefore you have a finished untrimmed brisket with 1/4" of seasoned fat over meat. Most dining guests logic " O' fat lets cut it off and not eat it" ok now that seasoning is wasted and your meat is only half seasoned. but by leaving a small amount of fat it melts away marries with seasoning and is deposited onto the meat still leaving "fat moisture" during the cooking proccess. I almost never put in foil and have a moist and firm (Not tough) finished product. Although last time after 6 hrs I put into foil for 2hrs then out again for 1hr, results were very good just on the verge of falling appart but still remaining intact. I prefer not to have my brisket fall appart that should be left for pulled pork. Just my 2 cents