Samsung calendar or Google calendar

I've been using the default Samsung Calendar since my first Samsung phone, the s5. (Seems like a lifetime ago.)

Never had any issues. I just restore all the data to each new Samsung I purchase. Smooth as silk.
 
Not at all popular, but I use the Calender from the BlackBerry Hub+ Suite.

But Samsung's calendar is pretty good

Won't use Google's calendar.
 
Google. No matter where I add an event, phone or PC, it shows up on the other one and syncs to my Gear S3. I'm one of those that uses my calendar for everything.
 
Samsung stock app. No need for other calendar app as it syncs with Google just fine. I don't see a reason to have two apps for the same thing.