Its a bit different to when I did it; i.e. there is much more flying that HAS to be done before you can test (when I did it, you did the test as soon as you were ready - CAA post 700hrs).
I called up the school to find out likely airfields and routes I would be using, and then flew all these procedurally in flight sim, as well as practiced holding with different winds and assessing my performance with the tracking. The 172 RG gives similar performance to a light twin.
You will not learn anything about flying flight sim, so use the automatics, then when you are paying X hundred per hour on the a/c, you will know your route / procedure inside out and not waste time / money on mistakes due to lack of knowledge. In addition, your capacity to fly the a/c should be improved.
I reckon so anyways....