You can use either to be perefectly honest.
I have ran with both, and from doing that I found that I like to run lump.
I use kingsford brand charwood lump. Mainly this brand since I got a heck of a deal on it.
The lump temps to burn hotter so it takes less coals burning to maintain a certian temp.
Also with the lump I seldom use any other woods for smoke.