I have the Otterbox Defender for the iPad Mini Retina, I specifically looked for the new version because I didn't want to take any chances. I do know of one difference at least: the new version has a hole for the additional microphone on the back while the old version doesn't.
The primary user of our iPad mini is our 4 year old son. He does pretty well with it and when I went to sell his old one on eBay there wasn't a scratch on it thanks to the Otterbox.
New Version
SKU Number 77-28157 (iPad Mini Retina or iPad Mini)
http://www.otterbox.com/iPad-mini-w..._color=20&start=1&cgid=ipad-mini-retina-cases
Old Version
SKU Number 77-23834 (iPad Mini)
http://www.otterbox.com/iPad-mini-Defender-Series-Case/apl2-imin1,default,pd.html