I smoked on a Weber kettle for years before getting my WSM last spring (never competed on it though). Never had any trouble maintaining temps, although it will require a lot more tending to than your BGE (you'll need to add charcoal about every hour or so). I've done ribs, chicken, and butts on it with no problems; brisket was MUCH trickier, as you have to worry about the placement of such a large piece of meat in relation to your coals, but it can be done (Bigabyte has a couple of kettle briskie cooks that he's documented in threads here). I always used KBB...but again, I never comped on it. Wish we had something like this around here; I think this sounds like a really fun comp. Good luck!
Good Batch BBQ Competition Team
Webers: 22.5 Kettle, 18.5 Kettle, and dual 22.5 WSM's
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