DEFINITELY, only children can develop into their individual selves. They do not have to contend with sibling rivalry, gamesmanship, and/or other forms of sibling drama. Studies have shown that children are routinely abused either emotionally, verbally, and/or even physically at the hands of siblings. There are some children who endure bullying at the hands of siblings.
Not all is bliss in the world of siblinghood. Rivalry is de rigueur with siblings as they are competing for the attention of two parents. The correlation of sibling rivalry increases with the number of siblings in the family. Siblings are also slated into rigid familial roles such as "the smart one", "the pretty one", "the stupid one", and "the athletic one." Such roles oftentimes last into adolescence, even adulthood and has either a positive or negative impact on the child involved.
Then there is the issue of favoritism and being unfavored in multichild families. An overwhelming majority of parents in multichlid families have favorite/unfavored children. Favored children are lionized while unfavored children feel as they are personae non gratae. Many unfavored children feel as if they are strangers in their families.
Besides sibling rivalry and favoritism/unfavored issues, there is birth order. Children in multichild families are treated either differentially or preferentially based upon their respective birth order. Oldest children are often treated the most harshly and differentially. They are held to tougher and higher standards. They are given responsibilities much earlier than their younger siblings at similar ages. Many have NO normative childhood and adolescence because of the numerous responsibilities thrust upon them. Middle children are well....either ignored, overlooked, lost in the shuffle. They are considered appendages of other siblings, NEVER recognized for their individual selves. Youngest children are the ones TREATED THE BEST. They have the most stress free lives, little or no responsibilities, and get away with murder.
Only children do not have to endure the sibling drama. They have time to devote to themselves without the constant interruptions of siblings. They can read and indulge in their hobbies in utter and complete peace. They have their friends over. They have peace, calm, and privacy in their home and personal environment. They are FREE in ways those with siblings ARE NOT!