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.

Thanks!