So I did 2 briskets in 48 hours this week. One on my large, and one on my FIL's new large. Mine was huge (17lb) and his was smallish (9lb). The large one was choice from the grocery store and the smaller one was "choice or above" from Whole Foods. Both were very well marbled and extremely flexible in the cryo. I did Salt Lick Rub on both which was awesome but salty. I did both around 260 grid and both were done at about an hour per lb. Faster than some but I attribute this to the heavy marbling throughout both (fat cooks faster than muscle). Setup was the same for both- v-rack over a drip pan. The large was filled with water, the smaller one was not. No difference whatsoever- they were both very moist and tender. No binder (mustard) was used on either and both had crazy crust, even after being wrapped in foil for hours before we ate. Both cooked over Ozark Oak with Oak chunks. Will use this combo on Brisket from now on. Great flavor for beef. Both came out as the best i have ever done and the people that ate them said they were the best they have had so I guess this flavor profile and time/temp work. I think I have found it and I'm not changing anymore!
The only other note I can pass along is that my in-laws had an electric knife. I ordered one as soon as I got home. It was so easy and smooth to trim their brisket I'll never do it another way again.
Anyhow, hope some of these tips help
Keeping it Weird in the ATX