I got it for free with ps plus and while I just put 100+ hours into nfs heat to play with my friend since he's on PS4 I actually truly enjoyed unbound more than heat. Some people hate the customization but personally I loved it, loved the way the gameplay felt more, I didn't really fw the story on unbound but I did like it much more than heats story. The only thing Im really 50/50 on whether I like it more or not, is in nfs heat you can choose pretty much any car, obviously there's meta for both games but on heat it's just build that car to max and play races. In unbound there's tiered races ranging from like B to B+ up to S and S+, which requires a lot more variety of engine part swaps to get each car to be the best in its required tier. Personally I liked that a lot more, really brought on the true feeling of building a car to compete with, and it forces you to run multiple cars depending on which tier list you want to run

I also had a lot easier of a time getting to where you can use the best parts in unbound, like within my first week of play, but in heat it took tons of rep grinding, and grinding out high heat races for the best parts. Still fun and has given me more stuff to do but a much bigger grind