JLB is clearly the more highly trained, more technically proficient singer, especially pre-injury. He struggles when he gets sloppy with his technique, and that certainly happens on occasion. I think BD is more consistent and is CLEARLY the better frontman, but his particular vibrato always bugged me for some reason and he has a tendency to go sharp (above the pitch). I'm a classically trained singer myself, and as such I tend to be pretty critical of vocalists, but JLB and BD are both pretty damned awesome.