Depends.

Horizon #1 is something in between Need for Speed and Forza. You have realistic racing on open roads and there is a lack of cops, but you also have the typical trashy drivers.

Horizon #2 is actually something else. While you still have the open world and the Forza 5 engine (on Xbox One at least which you should be playing instead) it is actually something more akin to taking the original Horizon, removing all the trashy characters, and adding in something almost straight from Top Gear. So for example, you personally drive to every event and can casually (read: not required nor do you not get anything for beating someone) to every event and you don't have challenges, you instead have a "Bucket List" with things like "Escape to the countryside in a Mclaren P1" (read: time attack with a stock Mclaren P1.) The first Horizon doesn't do this so extremely, but the second one really wants you to enjoy the moment instead of winning at everything as fast as you can. And again, play this one on the Xbox One instead as it uses a slightly modified Forza 5 graphics engine which is superior given the weather effects.

Honestly, pick up the demos if they are still up. They are pretty good representations of each game.