However in Most Wanted there are cops. Which make things more difficult. There are less features though that you can do to the cars in Most Wanted, no trunk audio, spinners, and the such. However myself I find the graphics have been improved.
The only difference between the black edition and the normal edition is you get a DVD with the black edition of behind the scenes stuff. How they used real people in the cut scenes and things like that.
If you liked NFSU2 then NFSMW is something you will enjoy as well. Have fun.