From somebody who has played Call of Duty on both consoles, PS3 is by far much, much easier than 360.
I had a 9.XX KDR on Black Ops 1 only playing Domination + Search, and 5.34 I think ( might actually be a bit lower ) on MW3 only playing Drop Zone & Kill Confirmed.
While I can only keep 2.0 KDR's on every 360 CoD I've played.

CYANERD!
/e:
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PCENERD