Hard drive

Ok as in my other thread i had a recent hard drive failure.I lost all the data on it and im pissed.In future i intend to back up my data.So far iv both a 250 gig wd passport and i intend to get another larger hdd for backup.I was intending on either getting either of these but was wondering is there a difference between them and what is the plug connection in both of them.ie 3 or 2 pin plugs.Any advice and or links to cheapers websites for this hdd would be much appreciated.The one im interested in is at http://www.pixmania.com/ie/uk/638806/art/western-digital/my-book-ii-essential-edit.html and http://www.dabs.ie/ProductView.aspx?Quicklinx=4TJL&CategorySelectedId=11157&PageMode=1&NavigationKey=11157,396720000&InMerch=1