Something else to consider if cooking for a crowd (I've done brisket for 200 - not a record but enough that I HAD to pay attention to yields!).
Packer brisket will only yield about 50-60% - in other words a 14# will only give you about 7-8.5 pounds of usable brisket. Flats yield about 70-80%. So, ulitmately the cost per serving is pretty close - at least in my area :D
All that being said: I'd use a packer brisket if I could get them at the prices TK, Jorge, etc. are quoting. I can't! So I use $2.12 per pound flats.
The "argument" is really not about flats vs. packers it's about doing brisket at all since the effort is really about the same. I love cooking and serving brisket because it's a challenge. Fortunately I do good brisket - even my marginal efforts (usually when I've got time restraints!) are very edible and the meat is fork tender.
So, read up and go for it. The technique for cooking brisket doesn't change except to add some fat (bacon) and mop/spray a little more often.
Southern Brethren BBQ Competition Team
"It's all about getting paid!" - Myron Mixon
"I love being hated in my hometown!" - David Hair
KingFisher Gator Rotisserie cooker, WSM, Stainless 5 burner with IR gas grill, Turkey Fryer, Weber JD Commemorative grill, slightly used Bandera chamber for future use as a cold smoker, Masterbuilt 40" insulated ELECTRIC smoker