No, as long as the functionality is the same or comparable (I am not familiar with the plugin's use).
Edit:
A bit more detail may be appropriate here. The extensions
* work as advertised right 'out of the box', but allow for detailed
custom settings. They are also under continuous development and see regular updates. That said, updating 32-bit Macs like ours is not particularly straightforward, as installing the latest update directly may (and in our case will) crash Safari. To prevent that you need to re-install version 2.4.1 first, uninstall it, and only then install the latest version.
As a user of the Webkit plugin you should be able to assess how its functionality and configurability compare with those of the extensions.
*) There are actually
two related extensions, ClickToPlugin and ClickToFlash, the latter of which represents a special case of the former. This allows for control of all plugins, not just Flash.
