Url Rewriting vs. Routing

I am making a making a new asp.net web forms site and would like to beautify my urls – I want to accept a url like this one “www.mysite.com/1-2,3” and turn it one like this “www.mysite.com/page.aspx?a=1&b=2&c=3”. Which option is best for this task – IIS7 Url Rewriting or Routing in terms of performance and ease of maintenance. Btw I am planning to use medium trust shared hosting IIS7, maybe 6.