Отсутствует. Assembly.CreateInstance фактически вызывает Activator.CreateInstance изнутри.
Использование рефлектора в Assembly.CreateInstance:
public object CreateInstance(string typeName, bool ignoreCase, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
{
Type type = this.GetType(typeName, false, ignoreCase);
if (type == null)
{
return null;
}
return Activator.CreateInstance(type, bindingAttr, binder, args, culture, activationAttributes);
}