What you prefer in the CV an employee who worked in many places but he didnt stay long or an employee who stable in his job?

Definitely a stable employee as it increases the chances of having better specialised experience rather than incomplete experience in different environments.

An employee who stable in his job.

Depend on company, if they need him for temp work they won't care of course

If they will need him for full time job for a long time projects, they will ask him about leaving reasons