It's like a completely different world. The rally physics of GT have always just felt like tarmac with a lower grip multiplier. If you play a real rally game you'll actually feel the car biting into the loose surface and gaining grip so you can properly take corners at speed and not just slide to the outside like you're on ice like it's always been in GT.
That's not even taking into account the completely different experience actually driving on narrow rally tracks with hazards constantly there to ruin your day. Trees, rocks, ditches. Not a solid unbreakable bit of tape lining the tracks which are wider than a highway.
It's quite the challenge driving cleanly for 5+ minutes, and as I say, worlds away from GT.