In terms of development, what capabilities does Google Earth Plugin have over Google Earth?
Google Earth can display a number of file formats, which may be generated programmatically, but in general the user controls the interaction.
The Google Earth Plugin can use the rich set of tools available for web development, and allows DOM manipulation of the data used within the earth environment. You can interact with the user environment, modifying the layers and how they are displayed.
I think with enough tweaking you can achieve almost anything that one can do in the other, but you might be pushing limits of edge cases. In more general terms, I think one difference is that the Google Earth Plugin can be programmed, and Google Earth is a viewer.
In more detail, Google Earth is a viewer of KML/KMZ files and data layers. Because layers can auto-update (based on time, viewport, location, etc.) you can achieve some advanced features. Because you can record and then play back, you can also make "movies" in Google Earth.
On the other hand, the Google Earth Plugin can be much more interactive, or even active without the user input. It is easier to push data using asynch client/server techniques, manipulate the DOM, etc.
I'm not sure what 'In terms of development' means here, do you mean 'for developers'? I'm assuming you don't and that you just want to know what capabilities the GE Plugin has over the GE client.
Adding to what has been mentioned already:
- Google Earth can be thought of as a Geo-Browser and it has a lot in common with the Netscape browser of old in that it allows limited capacity to create KML and KMZ files - an analogy for html. E.g. it has a 'create tour' feature where you can define your own flight around Google Earth but to use the full capacity of KML you have to manipulate KML directly.
- Comes with a canned set of layers (Oceans, weather etc)
- You can create your own network links which can be programmed to update in a given time.
- It works as a simple GIS as you can open multiple KMZ files and arrange/combine the layers in the places column.
None of these features are available in the plugin but you can view tours/network links and all other KML features and use other GE features like navigating.
However, the plugin has features that the client does not have:
- It can be programmed which means you can simplify the interface the user sees - helpful for non GIS users.
- Using this widget you can add tours to one without needing to do any code.
- Adding the plugin to a web page has the obvious advantage that you can embed it in text such as an article or and explanation of the data it contains.