The reason it's so slow is that it's downloading a lot all at the same time. It has to download the models for all of the 3d buildings, Disney has included hills and slopes that have to load but are hard to notice, and almost all of what you see on the 3d buildings is made up of a bunch of different pictures, which it downloads for the whole area, and when you zoom in, it downloads higher resolution. It takes a lot of RAM on your computer to store it, so the people who see it fastest will have a lot of ram, a fast processor, and cable internet without a bunch of other file transfers going on.
There seems to be a "memory leak" when viewing the 3D buildings, meaning it takes up more and more memory without freeing up the memory it's actually done using, which it doesn't know it can use again, so if you don't have a large amount of memory to start, it will fill up and your computer will have to start keeping that information on your hard drive temporarily, which takes more processing power... I'm sure google is working on improving it.
To make it faster, close it and re-open it if you're going to go to a different park. you can bookmark the parks, then switch off the placemarkers so you can still click them to get there but they won't get in your way when viewing or taking screenshots.
If stuff still isn't loading good enough for you to take a quality screenshot, try leaving it alone for a while, don't use your internet connection for a while and let it load. when you come back and it's loaded, you can look around better to get the perfect shot framed right, cause it won't have much if anything to load
).
On google earth, not so much.
