YES the values are not the same depending if you are using Symbolic Links or not.
When you are using dirname( __FILE__), you are using the physical real location on the disk and your are not using the symbolic links path.
If you have a problem to find the "params.ini" file, you have to search in another place and for sure, don't touch this file.
If you are not able to have the correct "params.ini" values, this mean that you don't use the standard joomla framework but using a "template company" that has bypass the joomla framework.
For example, if you are using YooThemes, we publish a plugin to patch their framework.
There are also patch for Rocketthemes and Joomlart.
If you want that we have a look on your environment and try to fix your configuration, this is possible with our billable support that you can order at
www.jms2win.com/en/joomla-multisite?page...35&category_id=1