Chicago. They have Salvatore Cecola in LV, but he has pull in Southern California, and Mesa Arizona. Rocco Lombardo is mentioned a lot but he mainly states in LV. They are not as powerful as they once were, but with the FBI having other priorities, the family is rebuilding both in membership and power. They have Angelo down in Miami who I had believed retired, but a rumor has surfaced that Angelo spent a weekend in Cuba having a meeting with Cuban officials. They also have pull in Dallas, Milwaukee, Denver and Kansas City.
Boston is in the papers a lot these days and most people will say they are more powerful then Chicago.
Detroit still has juice and is the subject of many debates but most of their power left them when many of their veterans passed away, and harsher business restrictions.
All three families have some breathing room to make new members as the FBI is going more after terrorists then the crime families.