IMHO the ideal slicing temp for a brisket is 195 - 200. I usually pull them at 190, foil them, wrap them in a towel and transfer to an Igloo cooler for an hour. The sitting time will allow the juices to settle and the foil help prevent the juices from running out. I know a guy who foils at an internal temp of 160 and finishes the briskets, in foil to a temp of 195. The theory is that meat stops taking in smoke at 160. The foil prevents moisture from escaping for the remainder of the cook.
Other factors to consider:
Quality of meat? Always go with USDA Choice or better. Look them over...I like a packer with an end (thin end) that's at least an inch thick.
Size - my preference is 12 lbs.
Smoker temp - you didn't say. 225 o is the norm for most folks.
Rub - a salty rub applied more than an hour or so will extract moisture from the meat.
Slather - some cookers swear by them. I mix 1 part yellow mustard with 1 part Miracle Whip and lay it on (top, sides, bottom) pretty well...and sprinkle the slather with my rub.
My .02 Hope that helps.