MVC URL structure with URI parameters

When creating routes for your MVC web application I have seen two possible ways to pass variables to a controller method:

With the first approach the variable is passed to a parameter of the controller method and utilized as such:

1a. http://ift.tt/15adv6v

1b. class controller1 extends main_controller(){

      function method1($var1){

         echo $var1; //prints "variable1"

      }

    }

The next approach uses URI parameters and allows for the name of the variables being passed to appear in the URL:

2a. http://ift.tt/1zwHpiT

2b. class controller1 extends main_controller(){

        function method1(){

            //split the uri into an array using framework function
            $uri = $this->uri_to_assoc()

            //call the uri variables as array indexes
            echo $uri['variable1']; //prints "34"

            echo $uri['variable2']; //prints "56"

        }         

    }

My question is concerning when to use one case vs the other? My guess would be that approach #2 would be more for RESTful web services while approach #1 would be for a web application that will be serving html and crawled by search engines?