I can only base my opinion on watching videos and seeing how real cars behave vs what's going on in the game(s), so take it for what you will. For example, the Escort Mk2 on gravel. It's going to be sideways quite a bit (or at least want to be), a lot of counter steering, a lot of on and off the throttle. In DR, the only time you really have to take care is around very tight corners. Aside from that it feels like driving a group A car. Flat out, no real concern of the rear getting away, little counter steering needed. On the other side, rbr, it seems like you have to be a damn alien just to keep it on the road (and pointed in the right direction), let alone drive it competitively. At least with this car, I think the best would be a mix of DR and RBR.
FFB, for me it's hands down still RBR. There's so much more feeling of the car and road in rbr than in DR. I've tried the recommended settings, setting things to the max, setting them low. It feels, unfinished maybe? I can't feel the front lose grip in DR, it's easily noticeable in rbr. If I don't play DR for a couple days or so, the first time back it feels weird, I have to get used to it all over again. Where as in rbr, I can play after not playing for days and it feels fine.
The engine braking is another thing too. In the Mk2 on Dyffryn Afon, you don't need to really touch the brake at all until you get past the first split, when you come up to that immediate/deceptive 2 right (can't remember exactly what the callout is).