Which one should I buy? this or Colonies?

[gr1mR36p3r]

Hi there Guys :)
title says it all: I was planning to buy the whole serie and play them all in order, when my eyes caught sight of Extreme conditions Colonies
so question, what does colonies add to the original? is it a dlc or a complete game? sorry guys I know it may be a stupid question but I am at work multitasking!

[Vyr'sai]

Colonies has two new single-player arcade modes and new multiplayer maps, gametypes, weapons, characters, and balancing. There is also cross-play with 360 players. The multiplayer of the original and Colonies are separate. I would suggest buying Colonies, especially since multiplayer in the original is a hassle.