With all due respect, I do not think that most people suffer because they choose to.
Well let me initially stop you right there, because "plenty out there" != "most", so you appear to be mistakenly presuming my position to begin with.
There might be a few people who are masochistic but most people suffer because this world is a storehouse of suffering, more for some people than for other people. Some suffering is within our control and other suffering is not.
“O thou seeker of the Kingdom! Thy letter was received. Thou hast written of the severe calamity that hath befallen thee—the death of thy respected husband. That honourable man hath been so subjected to the stress and strain of this world that his greatest wish was for deliverance from it. Such is this mortal abode: a storehouse of afflictions and suffering. It is ignorance that binds man to it, for no comfort can be secured by any soul in this world, from monarch down to the most humble commoner. If once this life should offer a man a sweet cup, a hundred bitter ones will follow; such is the condition of this world. The wise man, therefore, doth not attach himself to this mortal life and doth not depend upon it; at some moments, even, he eagerly wisheth for death that he may thereby be freed from these sorrows and afflictions. Thus it is seen that some, under extreme pressure of anguish, have committed suicide.” Selections From the Writings of ‘Abdu’l-Bahá, p. 200
Nah, check the Valleys, suffering is within our control, even if it is not by choice. Our Faith contains within it a mystical path to contentment, so the tools to end suffering are within our grasp, and according to scripture, it is even our duty to attain this contentment:
"The world has never had nor does it now possess stability (thabát), notwithstanding the complaints of some unfaithful and wavering souls. But, in truth, whatever takes place is well-pleasing, for the divine wisdom has ordained it. Without His command and will, not a leaf can stir, and whatever occurs is conformable to wisdom. All must be contented with it, nay eagerly desire it. However, in some cases, such as when the sweetness of reunion gives way to the bitterness of separation and, likewise, when, by the decree of remoteness, nearness and meeting are banished--this causes sighs of sorrow and grief to be upraised and the tears to flow. Otherwise, the matter is as some of the philosophers have cited from the words of Idrís: 'It is impossible for the realm of creation to be better than it already is.'" (Tablet of Bahá'u'lláh)
I would say, given the tools at our disposal, that it may not be a choice to suffer (though there are some who do choose to suffer), but it is a choice to not suffer.
So the question is, why does God allow some people to suffer so much and others hardly at all.
My question is "is there really such a disparity in suffering between people??"
Suffering is a subjective thing. Just as a man who leaves a sauna into a room-temperature room will call the second room "cold" while a man who enters that same room from outdoors in a blizzard will call it "hot", what is considered a cause of "suffering" varies from person to person.
As Fasting has likely shown you, the suffering one endures lessens each day as you gradually become more and more used to eating only when the sun is down. There are those completely content in conditions of abject poverty, and there are some people who seem content in conditions that would seem horrible to our subjective gaze. "A lover is he who is chill in hell fire;" (Poem of Attar quoted in Seven Valleys)
Likewise a man who is raised in extreme privilege isolated from discomfort will find true suffering in even the most petty of inconveniences. Compared to other things, first world problems seem minor and minute, but to those who don't know better, those problems are causes of real suffering. How many rich elites kill themselves out of depression despite having more luxury and comfort than most can ever hope for??
It seems that those who have more reason to suffer suffer less from a single event than someone who has less reason to suffer suffers from a similar event. So I'd find it impossible to measure and quantify who suffers more and who suffers less, given that the entire nature of suffering is subjective to begin with.