Not weaker PHYSICALLY. Anybody's who read more than 1 avengers comic knows that Thor needs Mjolnir to fly. This is basic, it doesn't bring any more to the discussion. Rage's point is that the hammer doesn't give Thor any kind of physical boost.
If I hit you with a hammer and then my fist. Which do you think would hurt more? Perhaps it wont boost in base strength, but his damage will increase dramatically.