you can also turn your diamond into a wifi router using wmwifi for more info you can go here>
http://wmwifirouter.com/. i'm still on the trial, and am considering buying it if I can figure out how to get it to work with my ipod touch.
other than that, usually wifi is faster than 3g, a lot of times its not a mig difference, but it can come in handy when streaming video.