AI do not think that suffering is the best way to develop character. Suffering can break and ruin people, make them heartless, cruel, spiteful, resentful, full of fear and unwilling to love. While some people do develop positive traits that were tempered in their hardship, I won't agree that the same person could not have learned the same lesson another way. For example a child of a wealthy family is taught values of philanthropy. On a family vacation at a resort, he is profoundly impacted by the sight of a child with a cleft lip begging. He finishes med school and spends his summers working to train third world physicians how to repair cleft palettes. What character advantage does an empoverished child with a birth defect have over him... suffering yes... but I don't think the son of privelege is missing out because his life was blessed. If there was a way to measure these things, I think you'd find as many genuine evil people who have suffered, as you would genuine gold characters who have not.
Suffering can lead to deep compassion and commitment to act with kindness and justice but it can also leave a person so deeply wounded that they are unable to function well in life and unable to trust or love other people.
A life of comfort and privilege can leave people shallow and oblivious to the reality of other people but it can also give them the tools and energy to do great good in the world.
There are people who suffer greatly but have strong supportive relationships around them and/or the personal or external resources to cope with the suffering. Then there are people who may have a lesser degree of suffering but no resources (inner or outer) to help them adapt and they come through a relatively minor experience less able to function and contribute to society.