I think bilinguals have excellent ability to solve problems because bilinguals see things from different two viewpoints and have flexible thinkings because of speaking two languages.
Also, according to Canadian research team, bilingual suffer from dementia five years later than monolingual.
Moreover, bilinguals can talk to people whoever speak languages which bilinguals can speak without hesitation against monolingual cannot talk with people who speak expect their native language.
These are points that bilinguals are better than monolinguals.