1) The way that the tooltips are displayed are different. I use wowheads tooltip library exclusivly.
2) this mod uses the ItemStats from
http://itemstats.free.fr/ to do the brunt of its work. I wrote my own retrieval, cache and http processing code. because of this my entire mod takes up less than 30k of code. the mod in this thread is a 1.5 meg download i believe?
3) This mod may be (for the moment) better suited for those people who run things such as EqDKP
4) This mod caches everything locally. Good if Wowhead ever goes down, this is good becuase you've cached any of your existing items and icons. It does use your own bandwidth/server resources to serve data that wowhead.com is allowing anyone to stream from their web services for no cost at all.