On the contrary, it's precisely like watching a 70" if the ratio of the viewing distances is equal to the ratio of the screen sizes. Simple geometry.
That's why I said "real world impact" (do you even HAVE a 70" to compare?). If I hold my iPad Air up a foot from from nose, THAT is a more accurate approximation of what the image looks like on my 73".
I'm sitting on my couch testing it. You can math it all day long, a Mini isn't cutting it at a foot, esp with a 70" at 9 feet. I'm at about 10-11 for a 73 and it takes an Air at that distance to begin to approximate it.
But then again, this a ridiculous discussion.
That said, it's all a trade-off of size v convenience. The rMini is literally the same thickness so it's just the diff in weight and screen size you have to decide on. The Air was close enough that the mini wasn't enough of a convenience to give up the screen size.
To each his own.