The person who started this debate is probably refering to the stereotype, introvert being anti-social and quiet, and extrovert being social and talkitive. See I grew up an introvert and my brother the exact opposite, he could make friends easily, the one thing I find funny is he is so social he often tells on himself without noticing it. So for that reason alone I think an introvert is better.
Introverts and Extroverts are just differently skilled and both are great assets in their own ways. Introverts can create new ideas and inventions while extroverts can inspire and motivate others. (As long as they have the right social skills). Both need to work together in order to work.
As Carl G Jung put it "There is no such thing as a pure introvert or extrovert. Such a person would be in the lunatic asylum"
According to the Merriam-Webster Dictionary, the word better means something is higher in quality, more skillful, and/or more attractive, appealing, or useful. A person cannot say introverts all have the exact same qualities (except for shy and quiet), so a person cannot say introverts are better or worse than all extroverts.