I've found some few directory script provider : http://www.reciprocalmanager.com/ http://www.wsnlinks.com/ http://www.boonex.com/products/barracuda/ http://phpweby.com/software/dir hope this gonna help you little bit.
Hi, Check esyndicat.com. We offer free version with limited functionality. Anyway, it's has all the tools to build powerful directory site here is the demo: Free Directory Script Demo BTW, Barracuda from the list above is obsolete. They don't provide that script anymore
Check This Out http://www.phpmydirectory.com/demo/index.php You will like it. Check This also : http://bizdirectory.co.in/backlink
I don't think you will get a comparison list anywhere. I think you should check both demos and play with these both version to understand what's more convenient one for you. Basic functionality exists in both scripts, but if you need extra you can go with the paid version.
There was also a plugin for wordpress that let's you make your wordpress a directory. And you can make it auto approval also.
Site sift, it's not bad but the developer has not yet updated the script for years. http://scripts.site-sift.com/
I am using phpld for about a year now and its working fine never tried any other directory script because never feel the need to test one Yea, sometimes its real pain to locate free pluginns for added functionality but phpld is still worth it