A while ago, I posted on the annual cycle in the difference between UAH and RSS.
http://climatechangeskeptic.wordpress.com/2008/08/13/rss-minus-uah-a-revealing-analysis/
Looks like Lucia, Atmoz, and McIntyre beat me to it by a few months. Here’s a post on Lucia’s Blackboard with a little more statistical sophistication than mine; note the discussion in the comments.
http://rankexploits.com/musings/2008/uha-vs-rss-temperature-differences-why-energy-at-1-year/
