The major structural difference between chromatin and chromosomes is that the latter are

The major structural difference between chromatin and chromosomes is that the latter are more organized and condensed.

Explanation:

Chromatin is genetic material packaged into a complex by special proteins (histones). That complex is in the form of uncoiled structures, so chromatin fibers are long and thin. Chromatin structure is permissive to DNA replication, transcription and recombination events.

On the other hand, chromosomes are highly condensed structures of genetic material that are formed just before the cell division.