Nexus 4 has 4,7 inch screen with 1.5GHz quad-core processor and 2GB of RAM. People from Google are saying that this smartphone has the fastest processor at the moment. Also Nexus 4, like Nokia Lumia 920, will have wireless charging.
Nexus 10, has a 10 inch screen with resolution of 2560 x 1600. The battery will enable 9 hours of watching movies. Also it will enable multiple users. You can choose users at the start screen before unlocking the device.
Also, there will be no 8 GB Nexus 7 devices. Google introduced the 16 GB version.
However Nexus 10 and Nexus 4 are not only new devices, they are pioneers of the new 4.2 version of Jelly Bean. The new upgrade of the operating system comes with a "Gesture Typing" which allows you to drag your finger on the screen when typing instead of writing as usual. Android 4.2 comes with "Photo Sphere" motivated by the Street View application, and allows 360-degree photos. New addition Miracast protocol allows streaming of videos from the phone to the TV, at the moment with Miracast Box, but LG announced integration with all of the TVs from the company that will come out in 2013.