Any charcoal will work in a
WSM, but people can be passionate about what they use. On one end of the scale are the lump only folks. On the other end are the Kingsford and briquette people. Folks say they can taste the difference between briquettes (more highly processed with the inclusion of additives) and lump (minimal processing but wood source can be ideal to questionable).
Lump definitely burns hotter than briquettes because there is more air space between the charcoal. If it is quality lump it will produce a cleaner, completely tasteless burn too, allowing maximum heat, which is great for smoking wood carbonization.
Briquettes are a matter of quality control and additives. I've never had an off taste with briquettes but many folks swear they can taste the difference. My wife is a "supertaster." She can taste things I never do. She has no problem eating meat cooked with briquettes and if there was an off taste I'd hear about it.
I've used several types of charcoal from various manufacturers in my
WSM. They all worked fine as a heat source. Kingsford Competition, which is packed to a very low density, lasts only about 50% as long as KBB. I tried one bag of Royal Oak Lump and it was great. The instant I opened the second bag of RO Lump, purchased at the same time as the first bag, it smelled like it had been soaked in jet fuel. It is sitting in my garage unused.
Presently I use the older formula KBB, aka Kingsford Blue (and white) Bag because it was inexpensive, delivered consistent performance, and I never had an off taste. Kingsford changed their formula in January, making the briquettes 7% less dense. In spite of what they say they don't last as long. Since I've recently changed to smoking everything hot and fast I'm contemplating switching to my favorite lump charcoal (Lazarri Mesquite), just using briquettes as a fire starter and a base to keep the smaller lump pieces from falling through my charcoal grate.
Experiment with what you can find, especially on sale. That's how I found the Lazarri. It was the end of the season and my local grocer had 20 lb bags on sale for $3.99.
Here is an interesting website that has a ton of information about just about any charcoal available, including briquettes.
http://www.nakedwhiz.com/lump.htm
