The structure on the right is likely to be lower in energy, since the negative charge is held on an electronegative nitrogen atom, and since a C=N bond replaces a weaker N≡N pi bond, so any interactions that allow this mesomer to form will lower the molecule's energy.
It will help if you can think, in orbital terms, about what you mean when you draw this resonance. What is the pair of electrons on the carbon atom interacting with to lead to the structure on the right? And what hybridization on carbon allows this interaction to be maximized?