And it's partially justified in people being used to being themselves. People have different skills, and with time they get used to them and learn to use them to the best while compensating for their flaws in some way. So after a while it comes naturla to consider our skillset to be the best one.
An engineer will learn to use his practical ability in a way that is not hampered by his lower theoretical knowledge. A scientist learn to use his teoretical skill without being hampered by his lower practical ability. neither would exchange position, because both learned to get the best out of what they have.
Sorcerers and wizards have different advantages. a sorcerer will use lots of times the same spell in a day and would never do with being able to cast it only once. a wizard will be used to variety and preparing for every occurrrence. if a sorcerer would get the powers of a wizard, he would learn 3 fireballs and 3 lighting bolts as his 3rd level spells and complain he can't dela as much damage as he used to do. or he would complain that after spending some spells in an encounter, he don't have them anymore and is out of good spells shall a similar encounter arise again. A wizard getting sorcerous powers would go crazy because he cann't prepare different spells in the morning if he want to pull out some strange combo. He probably would not think on casting the same spell 6 times in a row could be a good idea. Both adapted to use their powers at the best.
in the end, as xykon said, power is power. it don't matter much what form it takes, be it the chance to prepare different spells for each encounter or to cast the same spells multiuple times.