Once you a get a blue card in Germany, if you want to change jobs, you have to get a new job contract and apply at the immigration office for the job change if it has been less than 2 years since you got the blue card.
But in the eyes of the next employer, are you any different from an EU citizen in that they have to do some extra sponsorship or paperwork just for you?
The reason I am asking is, many companies refuse to hire people from outside the EU because they don't want to do visa sponsorship. But does this situation change once you have a blue card and are already in Germany?