I wanted to post this link to The Naked Whiz's database comparing a multitude of lump charcoal but didn't have time before I ran out of the house. Now that I'm back, here it is:
www.nakedwhiz.com/lumpdatabase/lumpbag11.htm
If you spend some time reading this database you will find out how true IamMadMan's statement is -- all charcoal is not equal.
In my teen years before I knew low and slow BBQ existed I chose briquettes over lump because they cooked longer and better on my little burger grills. When I bought my kamado last year I still had that old mindset, briquettes were better than lump, and just bought hardwood briquettes without added junk. I thought I was so smart, I picked up a bag of briquettes which was quite heavy, then I picked up a similar size bag of lump and it was light. I thought I knew everything I needed to. Several months later I found the Naked Whiz lump database and I read enough to understand where and what I had assumed wrong. Then I tried some good quality lump (too bad it isn't part of this database, it's King lump but not the BBQ King lump they reviewed). I learned that although lump burns quicker and hotter than briquettes in an "open to air" grill, it burns as cool and as long as you set it under the controlled air flow conditions of a smoker. That was my 'ahaa' moment and I've proved it in my own smoker this winter. In my kamado good quality 'light weight' lump burns longer than the good quality 'heavier' briquettes and produces even less ash. Length of burn is something to consider when comparing the cost of different charcoals. The ratio of very small pieces and dust (which is useless for cooking) to medium and large pieces in a bag of lump is also a factor to consider in cost. Some brands are notorious for including large amounts of useless small pieces and dust making them significantly more expensive than their sticker price.