I know some app developers say that I should uninstall then reinstall their app if experiencing problems or updating, but I wondered if stopping the app and clearing data via the Manage Applications setting would accomplish the same purpose. I'm running ICS 4.0.3.
The answer is no, you're not uninstalling the app by clearing the App data.
Clearing the application data is more or less resetting the application to an initial state before being customized based on the application settings, such as preferences, databases.
I am aware it sounds contradictory, but the crucial element is that the Dalvik cache has the pre-cached dex class within the Dalvik VM for the said app.
All Android apps have a dex bytecode cached in as a layout file embedded - the word is odex When the app is installed for the first time, the cache of the dex bytecode is loaded into the Dalvik VM's cache, thereby speeding up the initialization and execution of the app. Some ROMs are odexed, others are deodexed, if there's no odex file within, the Dalvik VM has to generate it - i.e. Slower at the start! When clearing the App data, that is in /data/data/pkg_name/ does not imply uninstalling! To uninstall an app, the Dalvik's VM cache has to remove the odex for the said app... –