I should mention that with the exception of things normally different between Black and White such as Black City, White Forest, the legendary focus and the appearance of Opelucid City, the two games are identical.
As aforementioned, the hack allows you to catch all 649 Pokémon in some way or another. This is unaffected by the version chosen to play; encounters are the same in both.
Every single trainer in the game has had their Pokémon edited, fitting a new level curve and increasing the difficulty overall. While not mind crushingly tough, they’re sure to provide more of a challenge than the original games were able to. The level curve takes full advantage of the new experience system in Black and White.
A vast number of Pokémon have had certain statistics about them edited. This can be a number of things, including experience rate, typing, base stats and abilities. A lot of Pokémon have been given their Dream World abilities as an option, where applicable and/or useful.
Pokémon have also had additions to their moveset, including additions or alterations to their level up movesets as well as TM and HM compatibility. Level up movesets in particular have been edited for 600+ Pokémon.
There has also been editing of many evolutions, generally involving those Pokémon who generally had to be traded to be evolved. Blaze Black and Volt White are entirely self-contained; no outside contact is required for anything.
Items found in the field have been changed considerably, to include TMs, evolution items and fossils previously only found post-League. The items have been adjusted in such a way that makes it convenient for the game’s progress. Where applicable, text has also been changed to reflect these changes. Multiples of certain items, such as the evolution stones, the Lucky Egg and the EXP Share are also given out, all in the name of convenience.
It isn’t just trainers and wild Pokémon who have had their levels changed; event Pokémon such as Reshiram and Zekrom have also had their levels changed, ensuring that they don’t become useless due to the sharp increase in levels.
All five in-game trades have also been edited, giving you new possibilities for your team.
A small number of attacks have also been changed to make them more useful, generally in terms of power (and rarely, type).
A number of documents are included with the download that allow you to see any and all changes made. Wondering what’s new? Where to find something? Consult the guides!