In dilemma of choosing supervisor for postdoctoral research
However I have heard a lot of nasty things regarding his treatment to his students.


If you think these rumors are true, do not go work for him.  If you work for him, you are endorsing his behavior and his reputation will impact your reputation.


  One of the offers was from my current PhD supervisor


There is a general expectation that a postdoctoral job should broaden your range of experience.  If your postdoc supervisor is the same as your PhD supervisor, there will be a perception* that you did not acquire new skills.  There may also be a perception that you did not move because you could not find a position that would broaden your skills.  It also makes it look like your adviser could not help you find a job elsewhere.

In summary, I recommend you keep applying for postdoc positions.  However, if you are one of the most famous institutions in your field, it would be acceptable to stay put, as relocation is less expected in this case.

*I do not endorse this view because it discriminates against people who are unable to move.  But I think it is a widely held belief.