All opinion I know, I have the Nexus 7 sitting side by side with the Mini and an IPad 3, just to say again, I think it is great the display looks far more vibrant than the 7, web pages appear clearer, the nexus is being sold !
I know Apple will release a Mini with retina soon its their dev cycle, but at this moment in time the Mini just does it for me, form factor display build etc.
I am no fanboy at all, I have had Iphones, windows Phone and Android phones, missus has a s3 I love all tech and think that the Mini is the pick at the moment if you use both the nexus 7 and the Mini back to back to me there is no contest !
Hope this helps somebody !
T