Difference between these 2 wifi shields

I'm trying to understand what the advantages of getting A000058 wifi shield (http://store.arduino.cc/eu/index.php?main_page=product_info&cPath=11_5&products_id=237) are over getting A000064 (http://uk.farnell.com/arduino/a000064/module-wireless-xbee/dp/2075343).

Any advice? There is a pretty big difference in price.

One is a complete package, ready to use. The other is a shield onto which you need to actually add the WiFi module (not included). Farnell doesn't seem to sell the WiFi XBee that you would need to use with that shield.