By having employer sing I-140, technicaly you are sponsored by employer, thus not a self-petition.
EAA and OR are similar, but also bear significant differences:
1. You can self-petition for EA, but not OR. Thus if your file your I-485 based on your EA (self-petitioned), you may change job as long as you work in the same field. For OR, you have to stick to the same employer.
2. EA is for people extraordinary in science, arts, performance, sports etc. So you do not need a Ph.D. to apply for EA. Many employer-sponsored EA filers are supermodels, actors/actresses and sports stars. A gold medal in a major international sports event is equivalent to a Nobel prize or a major Academy award, which is considered to be sufficent evidence for EA -- if you have one of these, you don\'t need any other supporting documents.
3. By definition,OR filers need to be outstanding in research, so they usually should have an advanced degree. But technically, OR filers need to prove their research project is most advanced in the US (with the help of their employer), they do not have to prove that they themselves are the top 1% scientists. Thus OR seems to have a slightly lower requirement than EA.
4. My opinion: if you think you can stay with your employer for at least 1.5-2 years, go with OR; otherwise, go for EA.