Rjovale,
This is all very interesting. I have only flown with AFPD and G3.5. Both are great, both allow you to edit the models to change the feel in the air. My mate used AFPD to test the CG positions on his turbine powered Hawk and F5, and the real world did in fact follow the results given by the sim.
I like features of both sims, in AFPD the 'fly over your head' graphics are well done compaired to G3.5, this is a bit odd in G3.5, BUT, I love the Virtual Instructor feature in G3.5. There are lessons in how to fly both basic and advanced manoeuvres for both fixed wing and Heli.
I have over 17 years with planes but only a year on helis. As you are only interested in planes I would find it difficualt to suggest one over the other. The controller that comes with G3.5 is much better than the one with AFPD, but you can save yourself some money and just get the lead to use with your own transmitter.
My mate mentioned above (hawk and F5) got AFPD last November. His 8 year old son has used it a lot since then. He had never flown a model in real life before. He soloed after 4 real world flights.
Bottom line, sims are good.

Enjoy whichever you decide on.