Positron himself developed the battle suit that allows him to channel bolts of anti-matter into fierce attacks. He used his powers to help defeat the Rikti, but at a terrible cost. Due to injuries he sustained at that time, he lost full control of his powers. Now, to protect others from himself, he remains imprisoned within his battle suit.
Yes, but probably not as much as you'd think.
Origin effects your shopping habits. Yes, shopping. When you get to higher levels and your looking to stock up on some dual and single origin enhancments you'll be limited to buying a certain kind of enhancement, which will only be sold from certain stores at locations throughout the city. Some of those stores at higher levels can be tricky to get to.
Origin also effects the "Titles" you can earn as you become more well-known by the people in Paragon. The title is basically another name that is added to the front of the name that hangs over your head. Think of it in the sense of "The Amazing Heroboy"...with "Amazing" being the earned title.
To a lesser extent, the origin you choose will result in you facing a certain group of enemies. If you choose a magic origin then you'll probably fight more of the magical "Circle of Thorns" than any of the tech or science foes, going strictly by the numbers. However, since you end up choosing a good deal of your contacts you can stray from that trend if you really wanted to.
The benefit is, once you get up to the mid and higher levels, magic foes are more likely to drop magic dual-origin and single-origin enhancements than any other type.
That's pretty much it. The choice is yours, like most everything else in City of Heroes.
Heroes come from many places. Some are born to power, while others seek it out. There are even those who have no special abilities, who rely upon technology or their own skills to help them fight crime. While they are heroes one and all, origins have an important effect upon what kind of hero someone becomes. City of Heroes presents five different origin types for players to choose from:
The Mutant was born with his powers. His innate abilities appeared either at birth or puberty. A rare few did not develop until adulthood. These powers set the mutant apart from the rest of mankind; they are capable of far more than any normal human being. Mutants are sometimes feared for their strange talents, but are more often admired by the public at large.
The Science hero received his powers either through purposeful scientific inquiry or through some accident gone awry. The hero might not understand the forces that bestowed his super powers; all he does understand is that nothing is the same anymore.
A technological hero uses gadgets to battle the forces of evil. No one else has been able to duplicate the amazing technology that lies behind these gadgets. This hero need not be a brilliant inventor; he can also be a normal guy who has received these gizmos from some benefactor.
A natural hero isn't "super" at all; his amazing talents are derived from intense training and innate abilities. He may have been guided since birth to become the physical specimen that he is, or perhaps some tragedy has driven him to seek perfection.
The magical hero receives his powers from a magical source. These abilities might stem from a mystical artifact that the hero has gained over the years - or perhaps the hero has mastered numerous spells that provide him with superhuman gifts.