PROC:
The Protective Response and Operations Committee is the administrative organization created by Paragon City's goverment in order to manage, direct, lead and monitor the other five groups. They primarily consist of beaurocrats and administrative personnel, and have very little to no field-presence. Their job is to oversee, not get involved directly. Since their formation, the efficiency and results of the other five Hero organizations in the city has improved, giving them a positive and respected public opinion. By default, regardless of which faction you join, you're a part of PROC as well, as your group answers directly to them.
DATA:
The Department of Advanced Technology Application. This is the faction which most heroes of a 'Technology' origin choose to join. DATA primarily focus on crimes, incidents and disasters that involve high-tech, cybernetic or electronic matters. While they have a generally good public opinion, there are those who worry that they're hoarding secret, highly advanced weapons and devices that could be abused or fall into the wrong hands. But for the most part, most citizens of Paragon City appreciate them and their work.
ELITE:
The Enhanced Logistics for Insight and Tactical Excellence. This is the group which most heroes of a Natural origin sign up with. As a faction that has almost no, or extremely few, actual members with 'real' super powers, ELITE is most often given the task of dealing with more mundane issues. Such as stopping regular terrorists, investigating criminal syndicates, thwarting the mafia and so on and so forth. While highly regarded as 'Champions of Every Man' by most of Paragon City, there are those who claim that the organization is vestigial and unnecessary, as everything they do could be handled by the other groups, and likely be done just as well - if not better. Still, among the general populace they have an overwhelmingly positive reputation.
GIFT:
The Genetic Investigation and Facilitation Team. The faction which most heroes of a Mutabt origin join. In fact, unless you have a mutant origin, you
can't join GIFT. Their primary duties involve locating, identifying and recording mutants and mutant behavior, as well as dealing with any incidents or situations casued by, or involving, mutants in general. As the opinion on mutants is mixed and varied, GIFT enjoys an equally mixed bag of opinions - with some people fearing or outright hating it, while others are intrigued and curious. GIFT is also a constant topic of online conspiracies and wild, unfounded rumors.
]MAGI:
The Modern Arcane Guild of Investigation. The team which most heroes of a Magic origin will join. This group is tasked with investigating and dealing with any paranormal or magic/arcane issues that arise within Paragon City. They're also tasked with securing, cataloguing and sealing away harmful or potentially dangerous mystic artefacts. As magic, in gneral, isn't well understood or known to the public, MAGI receives a usually negative and unappreciative opinion from the population. They're often blamed for any incidents or crimes that involve magic, or are accused to playing 'clean up' for things that they themselves caused - evne if if that isn't the case at all.
SERAPH:
The Scientific Experimentation Research and Application to Paranormal Humans. The faction which most heroes of a Science origin will decide to register with. They primarily deal with things that invovle scientific experiments, harmful waste of unknown origins or properties, alien technology or relics and things along those lines. While gneerally appreciated by most folks, some worry that SERAPH is just a playground for a bunch of mad, callous, unscrupulous egg-heads who'd create a black hole in the midst of the city, just 'cuz they could. Of course, that isn't true at all, but some people are just like that.
Notes:
Other then GIFT, your character is free to join up with whichever group they want, regardless of their origin and archetype. From a gameplay perspective, the groups are all pretty much the asme, and will just serve as where you get your "missions" or "quests" from. Their locations in the city is different, the aesthetics of their facilities are different and the NPCs you can meet and interact with from each group is different. But in the grand, non-detailed scope of things, they all serve the same purpose and functions, and you can do everything at the facility that any other group can, though as your own thematic version obviously.
Please do keep in mind that once you've made your choice and joined a group, quitting and applying for a different one is very frowned upon. Not only because it'll cause a lot of paper-and-administrative work, but it'll also require you to sign a bunch of NDA's and agree to a whole bunch of legal and beaurocratic fine print which may prove to be more hassle than it's worth. Plus, y'know, if you start over as a new member, you'll be put back at the bottom of the totem pole, where you'll need to work your way back up the Superhero Ladder in order to get to join more crucial or important missions.
But, hey, if you like signing documents, filing papers, being monitored and having to start off by stopping bicycle thieves and telling off graffiti-painting teens... Nobody will stop you.