Having played exhaustly GT5:P and now on my way to another exhausting play of Forza 3, Technically I'll give the edge to GT5:P in terms of sheer graphics, lightining and overall looks. Makes you really wonder, how further will the entire engine be improved when GT5 finally lands. If the Jeux France videos and TGS videos are any indication, it's that the overall feeling of the game has evolved a lot, and it wasn't even the final build.
When you look at other aspects, Forza is slightly better than GT5:P, in the physics department mainly, but that will be left for a true game to game comparison when GT5 lands.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
