The ability to drop pins is mostly a navigation tool, so you can then get directions to that point. Google Earth doesn't do directions.
The way I think of the two apps is this:
Google Earth is mostly an educational and exploration tool. A good app to use when you are curious about what's where and how it looks.
Google Maps is a navigation and service location tool. The better tool to use when you are looking for a business or how to get somewhere.
There is definitely some overlap, but each does different things better.
That said, there are ways to save places in Google Earth, though not on the iPad. Instead you use a desktop to create kml files which can be overlaid on Google Earth. The My Maps option allows you to sync these files between your desktop and iPad via Google. Again, this is mostly for education and other information sharing services.
I can't add much in the way of details, since I've never used it myself. The closest I've come was to export a KML file from Panoramio and view it in Google Earth on my desktop.
Good luck.