The smaller and cheaper pack opens up the Vanguard Jem’Hadar racial option and includes the dreadnought cruiser (a T6 ship), while the larger pack also includes playable Cardassians, several more Jem’Hadar ships, and several Cardassian intel ships. It’s expensive (like $120 of expensive), but if you really want to cruise around in all of the newest ships with the newest species options, it’s the obvious pick. Or you can just pick things up on the in-game store if that’s your preference, tradition is tradition.
Source: Official Site