Thanks Headroom for the answer.
I pretend to use arduino and the wifi shield for a mobile project. Using Wifi instead of ethernet would complicate the code so?
I've been seeing some code examples of wifi and it doesnt appear so hard 
At the beggining I wanted to use an GSM module and make the get and post trough GPRS, but not many people have done projects with that and the the complexity appear to be much more than using wifi.