Finisa Optoelectronics and Nande are both assistant engineers, which is more promising?

Assistant engineer is a professional title. You can apply for this title if your personal ability reaches this level. This is not a position. Many enterprises use this as the job title in order to make the recruitment sound better. If they are all such positions, they are basically not good. You can go anywhere you want to exercise. If you want a good income, these two positions are not so good.