I ditch the fat cap... I like that precious surface area for rub and smoke penetration! Butts are typically fatty enough, they don't need the cap to stay moist. Briskets, if they are quality cuts have fat marbled as well... and can survive without the fat cap. I always inject to hedge my bet on the briskets... but all that extra bark is worth the extra trimming IMHO. Neil can tell you he about fell over watching me trim out a brisket LOL