Will there be any difference if I login to my Magento admin panel by
I recently found that using localhost just won't work. Why this restriction exists is beyond me. You can either use the IP or create a dummy domain entry in your hosts file to use something like
Then when you type in http://dummy.magento/admin (if your store is installed at root) it will open the admin login page.
Remember to change these core_config_data values
BTW, I think this has been an issue since at least 1.4