Halo 3 or modern warfare 2 more appropriate for my 10 year old?

Of the two halo has less violence directly ociated with a relevent scenario to the world today. It's storyline can be more easily dissociated from reality while Call of Duty depicts blatent kiling of other humans along with a story line that can be difficult to handle emotionally considering MW2's story is loosely based on real world events. Although neither are appropriate for a ten year old in any way halo would be the lesser of two evils in this case. I love the COD franchise and own and play the series but the M (17+) rating is in place for a reason in this case :)