I'm a Sony man through and through and love racing games, but will never own an Xbox, so Forza is out of the question for me.
I am honestly not that fond of the regular Forza titles, GT is where it is at for me for the sims (despite almost any post-ps2 GT having some major drawbacks).
Horizon is more of an arcade experience, but it uses the mainline Forza depth to it's advantage (physics, tuning). Horizon 3 and 4 are really good, kind of hope Sony will take a look and make it's own open world racer but I doubt it.
I am a Sony guy as well, got a One for cheap (actually cost me nothing due to a trade-in of my old ps4, I got gifted a pro). Since it has backwards compatibility for many games I wanted to play, it was worth it for me.
One thing I dislike is that Sony closed both the studios behind WRC/Motorstorm/Driveclub and Wipeout. Dammit, Driveclub had a false start but eventually became great and that Wipeout HD collection is amazing, also one of the best VR games out there. Now it is just the GT studio. Well at least they are making GT7. But unless Sony invests in another racing studio, or expands on Polyphony, I doubt we will get more Sony racers than that.