All the mafia families started as street gang and for sure have a structure but with the prohibition and thanks to Lucky Luciano the families begane different from the gang.

First the division between associate and made man,the first can be non-italian the second must be full blooded italian;in the gangs for become a member must kill a people and the members age is very low even under 18;

Second in the mob for be made you must be a good earner or a stone cold killer (better if both of it) and usually the made men age is over 30;

Third the structure associate-made man and capo,you have your decina and take a share of the business of the men under you,and can be both white or blue collar crime,it's another difference with a gang that is involved only in street crime (drugs,murder,robbery ecc)

Fourth street gangs are visible and easily recognizable, use clothes with particular colors and tattoos visible even in the face, while the Mafia tend to blend into society and not be recognized.

Fifth the street gang members knows what expect him, or die young or end up in jail for a long time or for life, for which there are not many members of the crips or blood of 70 or 80 years, while the mobsters tend to accumulate money , to be able one day to retire and enjoy them; so they try in every way to don't go to jail for a long time because they know that the feds, will seize all the goods and money.