they are similar but with Android 8.1 they made a big change to how they handle calendar events compared to reminders.
on 8.1 a calendar event notification only stays in place for the duration of the event where a reminder notification stays until you dismiss it.
setting up reminders you have to use google assistant to set them up, your not able to set them up in a calendar, even though you can view and edit them in a calendar.
a reminder does give you the options for: day, time, repeat (daily, weekly, monthly, and yearly), and location. so there are a few less options but also gives you a persistent notification.
I didn't realize they haven't made an api for reminders. I have been looking into API.AI to see what it would take to use google assistant with VC similar to how it works with Autovoice. or how Amazon alexa works with VC
Autovoice integration instructionsso I can see what you mean as a pain in the but to work with.
It looks like adding a calendar event is going to be the best way to go, especially with no api to integrate with reminders
thanks