Between cosmids, plasmids and bacteriophage, which vector is more suitable for the developed of DNA chimera meant to be transformed into bacterial cell?
It very much depends upon the size of the chimera you are trying to create and what it will be used for. But for the vast majority of applications a plasmid is normally used.
Cosmids are essentially plasmids but able to clone large pieces of DNA (35-50 kB) because you are not limited by transformation efficiency. These used to be important for creating genome libraries. Bacteriophages also have very specialized applications.