diazonium salts of aromatic amines are more stable than those of aliphatic amines

The diazonium salt of aromatic amines undergoes resonance as shown below:

This resonance accounts for the stability of the Arenediazonium salts (or diazonium salts of aromatic amine). On the other hand, no such resonance is possible for diazonium salts of alipahitic amines. Hence, diazonium salts of aromatic amines are more stable than those of aliphatic amines.