Hi,
I'll try to answer every question:
1) Similiarities are that in general both extensions and macros let you have functionalities that are not available natively in QlikView (like writing back to a database, make transformations through regular expressions, etc). Extensions, besides let you create visualizations / graphics that are not available in QlikView (like gant charts, or some other cool visualizations). Differences basically are that Extensions run only in ajax client (or webview mode in desktop) and are made basically in javascript that can interact with other web technologies. On the other side, Macros are written either in VBScript or JScript and only work in IE-plugin or desktop.
2) You need to know VBScript or JScript and check the QlikView API, because not everything that can be done in a "regular" macro can be done in QlikView Macros.
3) Macros only work in IE-plugin or desktop because Macros need system access which cannot be granted in Ajax. Besides I think incompatibilites between ajax and macros.
4) This is a personal thought, but seeing what it's coming with QlikView Next, probably macros will tend to disappear and development will be towards extensions
5) Macros can give you functionality that doesn't exist natively in QlikView. However, they are very unstable and can make your applications slower. A recommendation would be using Macros just for extraction and transformation and not for final applications.
6) You need to know about javascript/html and preferrably about any other web language like CSS or any other script language so you can interact for example with web services.
7) Extensions work only in ajax client or desktop, because the way data is displayed in Ajax and IE-plugin is different, making IE-plugin unable to display extensions.
😎 The main advantage like in the case of macros, is that extensions let you create functionality that is not available natively in QlikView. Besides you can create custom objects like maps, gantt charts, interact with webservices, etc. The downside is that they will not work in IE-plugin and in order to visualize them in Desktop you need to turn on webview.
9) Performance impact can be seen when using macros, because they can cause that your qvw run slower or just crash without reason
10) For more details try to check the QlikView API and search for examples of extensions here in community. Another excellent resource for extensions is Stefan Walther blog: qlikblog.at
regards
