The iPad Mini is essentially a smaller iPad 2 and the iPad 2 has older hardware specs. What you're paying for is their tablet software library where they have 250K tablet apps to about 2K for Android.
I'd say that the Nexus 7 tends to need more maintenance than an iPad which is one of the reasons why I think that the iPads are better for kids.
Here's a link to the Nexus 7 forums at phandroid. People are talking about problems with the Android 4.2 upgrade. I personally have had zero problems with the upgrade but it seems that there are many out there that are seeing problems. In some cases it might be app/OS compatibility issues.