Frame rate drops in GT6 can be affected by the system and game settings (
https://www.gtplanet.net/forum/threads/gt6-framerate-depends-on-which-console-you-have.295306/). This is no different than AC settings on a PC. AC will let you pick settings that have low frame rates. AC does allow for more control so you can "dial-in" the best visuals for whatever computer you happen to own. The notebook I use to play AC cost about $1600. This is a far cry from how much my PS3 cost. My notebook also happens to be immensely more functional than a PS3.
As a test I attempted to create "identical" settings for a Ferrari 599 in GT6 and AC and then compared the experiences. I started with GT6, and then moved over to AC. My lap times on the Nordschleife were pretty close to identical in the 2 games (about 7 minutes).
- GT6 appears to be communicating grip through the Force Feed Back. AC is communicating body roll AND grip through the FFB. If I'm driving an "oldie but a goodie" car in GT6 I can feel weight transfer happening, but that feeling is not present in the FFB with the same level of sophistication as AC.
- GT6 has more options for customizing a vehicle. As an example: There's no "LSD" in AC, so there's no way to "tame" a torque happy vehicle. The 599 in AC was more likely to spin out the back tires, but I did eventually learn to compensate by shifting earlier and going easy on the accelerator.
- The car in AC felt looser at first due to the body roll, but after adjusting my driving style it eventually felt more stable, which I'm assuming may be due to the active wing on the 599xxEvo in AC (GT6 wing is static). Or it could just be a variance in how "racing hard" tires are implemented in the 2 games.
- The PhotoMode in AC seemed buggy. It did allow me to do a few things that GT6 won't, in terms of camera placement, but the textures got confugled at one point and some of the pictures were not what I had framed in the "camera".
- The vast majority of the track felt familiar between the two games, but there are slight differences. I'm curious to see if my AC experience feeds back into better GT6 lap times (and vice versa).
Playing video games to conduct strict scientific observation is a win/win in my book.