Well the 939 is faster. The big dif is upgradability. You will be able to use future processors once it gets old and upgrade, The 754 wont be able to do that.
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2065&p=8
You can check out the performance dif. Its faster but not by a ton.
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2065&p=8
You can check out the performance dif. Its faster but not by a ton.