Hardwood lump produces far less ash than charcoal briquettes, burns hotter, and, possibly cleaner. A basket or chimney full won't last as long even with good draft control, probably due to it's lower density per volume and that it's more difficult to get a full basket/chimney with odd-sized pieces. This can be overcome by shaking the lump into the holder to settle it in tighter, if it matters that much, but you will have lots of small pieces dropping out the bottom through the grate if you shake it.
Eric