Here’s a Video Comparison of Gran Turismo 5 and Gran Turismo 6’s Demo
DigitalFoundry has put together a video which compares the visuals and performance of 2010's Gran Turismo 5 versus the recently released Gran Turismo 6 demo.
Okay, so yes this is a comparison between a completed game and a demo, but GT5 didn't change much between its GT Academy demo and full release. You can expect better frame rates and some polish between now and release. For now, this is the closest thing you'll get to a fair comparison between the two releases until GT6's holiday release.
You'll notice that GT6 has several technical improvements. Color balance, environmental effects, and shadows are improved on the newer game. Despite this, they look eerily similar. If you're a Gran Turismo fan the major selling point will be having access to many more premium cars, additional tracks, and being able to load races and menus much faster. If you're hoping for a lot more you might be setting yourself up for disappointment.