Lump charcoal will light faster and burn quicker and hotter than briquettes. I use it for meats and veggies that I want to sear and grill quickly. If you intend to cook something like a beer can chicken, I would recommend briquettes. Lump doesn't work for low and slow.
ThrRoff gives some good advice here but you can use it for low and slow, It's just not as cost effective over the long haul but that's a personal choice.