i'm actually going to paste a comment about FH i made years ago as it's applicable to this question:

http://board.okayplayer.com/okp.php?az=show_topic&forum=11&topic_id=292445&mesg_id=292445&listing_type=search#292550

cars feel unique and different from one another, much like they do in more traditional sims like forza and gran turismo. this is the opposite of more arcade-ish racers like burnout and need for speed

the actual racing tends to be less punishing than sims and it encourages taking risks. the game places an emphasis on style, driving aggressively, and cleanly by rewarding the player with points for things like long drifts, consecutive passes, clean laps, etc. it's basically the kudos system from the project gotham racing series (a case could be made that the horizon series itself is an extension of the project gotham racing series)

there is a tuning system like in traditional sims but it doesn't go very deep. you can't change gear ratios or adjust your camber angle. it's a money sink, in a way. you can still do neat stuff like engine swaps and adding superchargers in addition to more commonplace things like suspension replacement and weight reduction. it's theoretically possible to modify a lower class car like a supra to the point that it is able to race alongside high end paganis and mclarens

like forza and GT, there are a lot of cars (about 200). it takes place in a contiguous open world, like burnout or test drive unlimited. it has the gradational difficulty system from forza and when you turn all the assists off it feels more like a sim than an arcade racer