407 will be the fastest by far (even during rush hour, providing there's no crash or anything, it moves around 120-140), but your rental car company will rape you with surcharges (on top of the 407 raping you for toll fees)

7 between Weston and Keele will be really bad during rush hour, take Rutherford or Steeles if you want to avoid the tolls... they're not much faster but at least they move.