I've been playing these two games whilst my internet was out. I was curious to see what they were like as I never owned the PSP versions of any of the NFS games growing up. They are very fun, albeit more limited on content than their PS2 counterparts. In some ways though, I geniunely prefer these versions. It really depends what you are looking for. I was never a huge fan of the open world aspect to Underground 2 and Most Wanted, it just felt like an extra added task to get to the races. Even though on paper it's cool to have an open world to drive around in, I generally just want to race majority of the the time. In these games you get taken straight to the races from the menus, it's very seamless and it still has the music and great customization from those games. They are great bitesize versions and are honestly more reliable when it comes to emulating. PS2 has a lot of hiccups sadly where the framerate can dip but the PSP is very stable and I was getting consistent frames with no dips once with these versions.
