if it makes a difference... Netflix on roku 3 allows the different viewer profiles where the 2 does not. so different family members can have their own watch-lists, and kids can be limited.
roku 3 is HDMI output only, but is ethernet and wifi ready. roku 2 has an a/v (3.5mm pin) and HDMI output, but is wifi only. It comes with the 3.5mm-to-RCA cable.
Roku 3 will also autoplay the next episode of tv series, then after so many it will stop to confirm you are still watching (like pandora). Roku 2 will pull up the next episode but you have to select play manually.
the UI is different between the them as well. i like the appearance of the 3's UI better, but with the hours i work I never get to watch tv on it.
and back to the channels and material available. roku has all the subscribed channels (netflix, hulu, amazon, vudu) also has crackle, popcorn flix, youtube, facebook pics and vids, pandora, iheartradio, several disney channels and PBS, twonky beam, etc. through the app on a device you also have "play on roku", allowing me to stream music on my phone to the roku to be played over the tv sound system
If i add another tv in the house i will get another roku 3 hands down. we moved to this house 1 year ago next week, and got both rokus within the first month.