The On the Brink expansion adds the following to the base game:
- More event cards.
- More roles.
It also adds the possibility of playing with 5 players and some extra challenges with their own set of rules.
If you are playing with 4 players, and no extra challenges, is the game strictly easier than the base game with no expansion?
The rules say that you pick
2 x #players event cards, so there's 8 event cards instead of 5.
Event cards increase the size of the players deck, and are usually very useful. A larger players deck means more cards between Epidemic cards and more rounds to finish the game.
I'm not sure if the new roles make the game easier of harder.