What is the difference in performance between these cards?
http://www.overclockers.co.uk/showproduct.php?prodid=GX-238-MS
http://www.overclockers.co.uk/showproduct.php?prodid=GX-281-MS
http://www.overclockers.co.uk/showproduct.php?prodid=GX-238-MS
http://www.overclockers.co.uk/showproduct.php?prodid=GX-281-MS