Is the iPad 2 any better at handling large PDFs than the original iPad was?
The iPad 2 is most likely to be faster than the original iPad as it has the newer A5 processor, which is dual-core and faster than it's predecessor, the A4. The iPad 2 also has 512MB RAM, which is 2 times more than the original iPad. This means that the rendering of the images will be faster, and more parts of the PDF can be stored in memory for a longer period of time, ensuring a smooth read.

This article also shows the difference between the speed of the PDF rendering and other factors in a 3rd-party app, but clearly shows that the iPad 2 is definitely faster.