Whenever you use a parallel structure, you can often omit words that are implicitly understood. For example, in the sentence, "I want you to get up, (to) get dressed, and (to) eat your breakfast," the word "to" is superfluous in the second and third elements of the series because it is implied by the parallel structure. In your sentence, "...who have been helped than who have not been helped," the words "who," "have," "been," and "helped" can be understood from the parallel structure. In fact, it is common to hear somebody say, "There are many more people who have been helped than not." I hope this helps.

The first answer is more right. The (been) is optional. The second answer sounds unnatural.