--Jeff--
He is extremely shouty during challenges, and also quite sarcastic sometimes.
--Chris--
He sets the most insane challenges which should kill the competitors. He also is not shouty or over enthusiastic, he just love's hurting people!
Round one goes to Chris
Round 2 - Elimination Ceremony
--Jeff--
He talks a lot, and also reveals a lot of game play sometimes.
--Chris--
He honestly just saves people, he never talks...
Round 2 goes to Jeff, since Chris never speaks.
Round 3 - General hosting abilities.
--Jeff--
He is rarely shown other than the marooning, challenges, tribals, and that one time he showed up to eliminate Dan. However, when he is on screen he is excellent at his job.
--Chris--
He clearly just appiled for the job to hurt people. He laughs at their misery and even refused to save an entire cast's life in Season 6. He has also been known to rig, e.g. Sierra's elimination in season 3.
Round one - Challenges