I've found that most brisket issues come from technique and nothing more. I've done plenty of Costco Choice grades, Costco Primes, and even a few Waygus from Wild Fork. All had similar enough results for me to decide it's not worth the extra money for the Prime are even Waygu, Choice is fine...and bbq is intended to be cheap, not gucci.
The method I've been using with great results:
I spray the brisket down with beef stock as a binder, then apply a very light dusting of Adolf's meat tenderizer (not for tenderizing, it really adds to the overall saltiness in the end), then a thick coating of my brisket rub. Into my pit at 275-285°. When bark is set, I wrap in butcher paper. Before wrapping I wet the paper by spraying more beef stock on it, then a little beef tallow, and wrap. It then goes back on until 190°, then off and into a long hold at 175° for 5 hours. Pull it from the hold, rest 30 mims, and slice.
This method gives a great result every time, it's the little details in technique moreso that grade that make a world of difference. In fact, I have a Select grade going on the smoker Sunday...local grocery store has them on sale for $2.79/lb. Did one a few weeks ago without realizing it was Select (never seen select grade at the store before) and it turned out just like any other brisket.