No offense kharmapolizei, but it is a good idea to run registry cleaner because they remove left over entries from uninstalls. There are very few uninstallers that remove all remnants of the program. I use a free third-party program called Revouninstaller which does a very good job at removing registry entries and files that still exist on the system. You can download it here:
Revo Uninstaller Freeware - Uninstall Software, Remove Programs, Solve uninstall problems
These cleaners use different algorithms to check the registry, that's why you get different results for different cleaners.
To protect yourself, always create a restore point before running any registry cleaner!!