When should I use the J!1.5 router - When Should I Use The J15 Router

Support Channels - When should I use the J!1.5 router

When should I use the J!1.5 router file instead of AceSEF extension
If you have an AceSEF extension for your component you dont NEED to use router.php file unless you dont like the URL rewriting of the extension in comparison with router.php's one.