The larger iPad reportedly features a 12.9-inch display which, as you can see in the video, is a substantial increase in size.
Earlier today a schematic leaked that claimed to detail the exact dimensions of the device. You can see that here.
Apple is expected to unveil the iPad Pro in the third quarter of this year. It will likely put a strong emphasize on its utility for enterprise, education, and similar areas.
Take a look at the video below to get an idea of how big the device may really be.