Yes new tires on your vehicle will create a smoother ride as they grip the road much better than worn out tires.
If your tires have 40,000 to 50,000 miles on them then it may be time to replace them with new tires regardless of age especially if the tread is wearing down.
When you replace your tires you get a better grip on the road, a smoother ride and better stopping power compared to old worn out tires.
The tread on the tires also provide the grip for the road when you stop so even if your brakes are good your tires could cause you to slide and not come to a stop soon enough.
If you're planning on going on a long road trip and your tires are in need of replacement you should replace them before the long road trip.
The new tires will also provide you with better gas mileage and make the vehicle handle better as well.