What do we compare here? Brands, OS or recent devices: Android vs. iOS? the flagships: Galaxy Note 8 vs iPhone X?
To provide an answer, we must define a characteristic and common element that can change significantly from mobile to mobile: battery, RAM, memory, size, screen quality, photo, physical keyboard, integrated pen interchangeability. Otherwise all smartphones make calls, provide SMS and emails with access to the internet and applications.
Then everything remains an opinion based on needs and prices ...