Dust 514 is what we could class as an MMO-FPS, because it allows for interaction with another MMO (Eve Online) and both games influence each other, to a certain degree. The interesting part of Dust 514 is the amount of complexity such an FPS offers. You have different skills and fittings, you can design your own "Class", based on the Dropsuits, Modules and Weapons you choose. Compared to the somewhat "rigid" Planetside 2 I am tempted to say that Dust 514 is closer to the original Planetside 1 than Planetside 2 ever was. This observation came from the one thing that Dust 514 offers, the "Complexity" of the classes. You are not just a "Sniper", "Assault" or "Medic". There are different things that you can decide to be... granted you have the Skills and the in-game cash to customize yourself.