As previously mentioned, Weber did (and may still do, I can ask the guys in the lab) used basic Kingford for ALL testing. 1) consistency, 2) availability to the public. At the time, Weber Heat Beads ran notoriously hot and quite pricy. Even back then, they'd send me home with bags and bags of Kingsford...
So I use what's on sale, usually a couple bags at Walmart is cheap. Sometimes some Royal Oak as a back up.
If you great once in a while, you're not going through a lot. I grill 3 or 4 times a week -I even gather up the half burned ones and use those.