It seems like the White Forest has some pokemon in it not available in Black, but Black City has none. What are the differences between the two places?
The difference is that white forest, you can encounter pokemon, black city you cant. The items are different also. Also in black city, you encounter more trainers with rare pokemon than white forest.
It's really complicated but in white forest, you can encounter a random number of different set pokemon every day.In black city you fight the trainer that have the pokemon. With the ability of high link you can connect with other players and get new pokemon that they have and you don't.