It must be eyesight differences, because I can easily see the differences in the non retina mini. I view lots of documents with equations and one needs retina for that kind of thing. For tablets, since i have tried most of them, the iPads just seems better implemented with more useful and polished apps...and that's why, in my mind, I can live with the mini (since I have a 3nd Gen already). But I want a retina screen mini. And since I got the LTE mini, my mini goes more places with me, unless at work, where I typically take my 3nd Gen iPad. BTW, when at home, my 3nd Gen iPad lives in a stand at my desk. I use it for viewing my photos. I have my Nexus 10 in a similar stand at another location. My Nexus 7 is gathering dust. I'm going to be looking to gift it to someone.
It is very likely that once the retina mini comes out, I will never buy another full-sized iPad. Actually, I don't see myself buying another full-sized iPad anyhow.