FWIW, I sure would hate to cook a brisket without burnt ends, so I always go with a full packer. But I will add this: last year, we were doing a practice cook and I asked the wife to pick up a brisket at the grocery store. Packers are hard to come by around here and I usually have to special order them, but our local grocer usually has these huge 9-10 Lb. flats...good enough for a practice cook...except...they had no more of these flats. She came home with this tiny little 4Lbs. piece of flat that I was sure was going to end up tasting like a shoe. So I used my normal method for cooking (hot and fast, injected with Butchers) and I was SHOCKED at how good the end result was. My guess is the Butchers had A LOT to do with it...but still it was mighty tasty!
I guess what I'm saying is...there's a lot of great advice here and there is no right way, so go with what works, try all the methods provided here and go with what you like best. Best of luck!
Mark aka Earl
Slower Lower BBQ
(2) 22.5" WSM, (1) 18.5" WSM, (3) 22.5" Weber Kettles, Super Fast Red
Thermapen, Stoker, Airline Cart!