Personally, for the money, I would get Real Traffic over Drive. Real Traffic comes with a basic car rig helper to get the vehicles ready for traffic simulation. As an industrial engineer who actually has programmed simulations of products queuing in a factory production system, the ability to accurately simulate cars queuing in traffic is NOT a trivial exercise. Plus there are all these other little hooks built into the program like tail lights and turning signals along with traffic lights. Honestly, simple animation of a car going down a street could easily be done by hand and a little bit of expresso to get the wheels spinning at the right speed. Now try to animate 100's of cars going down the highway at different speeds, changing lands, queuing up, etc. A bit harder task. Plus they just added a banking system for large trucks on off ramps.
I listened to the tutorials and the basic set-up seemed pretty straight forward.
Unless you are going to simulate off road driving or want to skid out at high speeds, I think you will get more mileage (pun intended) out of Real Traffic than Drive for the extra 20 euro's that Real Traffic costs over Drive.
Drive gives you one car doing 1000 abnormal things on the road....Real Traffic gives you 1000 cars doing normal things on the road.
Dave