In the case of the “new fourth generation iPad” there are very few differences. Compared to the iPad 3 (the new iPad) introduced just 7 months earlier, here are some of the significant changes and non-changes.
Display resolution: unchanged
Connector: 30 pin standard to the new lightning connector (8 pin reversible)
Core chip: A5X updated to A6X
Graphics core: Dual core to Quad core
Battery power: unchanged
Cellular: “4G” upgraded to LTE
So it is essentially the same iPad, with an updated chip and the new connector.