thinking of buying a Kindle keyboard WI 3G what is the difference between that?

[Anthony]

If your priority is book reading then I would recommend you to get the touch version but if your priority is typing and emails then I would suggest you to get the keyboard version,

The ads are headache to some peoples. They just don't like getting ads. So the version which claims to be without ads is better for those peoples only, but if you do not minds ads beside your page like the ads we get in Facebook, then you are good with that version.

Here is a very good place from my bookmarks where you can get more information on the differences via FAQ about kindle:

http://budurl.com/KindleRegularFAQ

And here is a good review for the differences between your mentioned versions:

http://budurl.com/ChooseKindle

Hope I helped!