The big difference is the location of the motor. When the motor is right next to you without a lot of insulation it is going to be a lot noisier than one 40' away. In my own personal experience of driving and owning both types over the years a rear engine coach is far quieter. By far. Most of that is due to the motor being far away, and some is due to more insulation to keep out noise.
My current coach is very quiet on a decent road. So quiet there is nearly no noise going 65 mph. You can listen to Mozart with the volume turned low.