I will agree the FSX rudder behavior is negligible, but that may be from having the auto-rudder feature on. If you don't use auto-rudder, then that is as good as FSX gets. Fortunately, A2A manages to build some great physics on top of what is already present in FSX. I could go into extreme detail, but have a look at some of the Accu-Sim packages A2A has created specially for their aircraft models, and check out the physics features they implement. Propwash over the tail, physics based sound, even some engine maintenance routines are in there. Realistic rudder behavior is just the tip of this iceberg.
Now I sound like a salesman
but, really, check out one of the promo videos detailing all this stuff and see the magic for yourself.