Im pretty sure Kimimaro can harden his whole body plus remember that battle with garra and the whole field of kimimaros spikey bones and how he could go through his bones X"D I say Kimimaro all the way spikes poke out all of kakuzus hearts X"D
Kakuzu. He pretty much has kimimaro's defenses when he hardens his body, has more raw power, and kimimaro's bones only defend against blunt force damage, they don't guard against fire and lightning.