Having spent countless hours on AFPD and Realflight G3 ( with the expansion packs, latest patches and updates ), I have to say Realflight G3 is ahead in realism - way ahead. All of the RF3.5 models in the expansion packs and add-on disks are extremely accurately modeled physics wise to the real-world counterparts.
Most of the downloadable AFPD and expansionpack models fly like helium filled foamies tethered to sky rails. However, there are a few 25-40% AFPD models that are very good, but the pre and post stall behaviour is still not there - far too forgiving. Whereas KnifeEdge (Realflight) is constantly tweaking and (usually) improving the flight models, IPACs (Aerofly) is focusing on its low end (easyfly) and the last few AFPD releases all fly the same surreal way. AFPD is showing its age and is overdue for a major overhaul which I hope is coming. The only advantage APFD has over Realflight is that it loads fast, uses very little computer resources and has more flexible control mappings should you wish to use your own controller.