Yes.. 1-2 seconds of 'much' faster with A6X processor.. Not worth for an upgrade while there is a possibility of testing a brand new different hardware in the market. There is nothing only iPad 4 can and Mini can not. Everything works with iPad 4, works with Mini as well..
if you don't count the seconds while Safari is loading a web page, you won't even realize how fast is the device and compare it.. The only thing which makes a real difference is Retina display and the biggest part of this 'faster' processor is working for this Retina.. Not for a completely better performance..