Here is a review that says the WCF12 did as good as the Socket from a power perspective (though they don't list the actual specs). They do list the specs of the WCF11 so that is at least a starting point (I believe the 12 uses less power than the 11)
http://www.pdabuyersguide.com/tips/linksys.htm
Here is one that says the Tx on the WCF12 is 250mA
http://www.tampabay2002.com/subpage.asp?subnavID=102
Here is a Socket review that highlights the power savings
http://www.pdabuyersguide.com/tips/socket_wifi.htm