What's the difference between these two StructureMap configs?
ObjectFactory.Initialize(x =>
{
    x.For<IBusinessRelationsContext>().Use<BusinessRelationsContext>().Ctor<string>().Is(ConfigurationManager.ConnectionStrings["BusinessRelationsContext"].ConnectionString);
    x.For<IBusinessRelationsContext>().Use(_ => new BusinessRelationsContext(ConfigurationManager.ConnectionStrings["BusinessRelationsContext"].ConnectionString));
});

public BusinessRelationsContext();
public BusinessRelationsContext(string connectionString);
public BusinessRelationsContext(EntityConnection connection);

ObjectFactory.TryGetInstance<IBusinessRelationsContext>();

x.For<IBusinessRelationsContext>().Use(_ => new BusinessRelationsContext(ConfigurationManager.ConnectionStrings["BusinessRelationsContext"].ConnectionString));

x.SelectConstructor<IBusinessRelationsContext>(() => new BusinessRelationsContext(""));