Having objectives in a stage system makes the game more fun since you have a more concrete goal. That said preventing the granny from getting hurt is sometimes kind of tough/annoying if the leash gets caught on a prop if you slingshot the granny too far by accident. I found level 4 easier than 3 since trying to avoid people and avoid the granny from hitting objects (including those people you're avoiding) required a lot more finesse compared to just running for the goal bowling people over. I didn't finish level 5 since I didn't really remember where all the hydrants were and didn't really want to go back and look for them in level 1/2.