When comparing Calendar vs Batman, the Slant community recommends Calendar for most people. In the question“What are the best custom Android Wear watch faces?” Calendar is ranked 20th while Batman is ranked 49th.
Question Ranking
Pros
Pro GNOME Native integration
Pro Synchronisation
It has online accounts integration.
Pro Currently in active development
GNOME Calendar is improved with every release cycle of GNOME.
Pro Simplicity
Calendar for GNOME aims to find the perfect balance between features and usability.
Pro Big time and date
This is a functional watch face. At just a moment's glance you can tell what the time and date are.
Pro Cool
It's a Batman watchface which is super cool among a certain crowd. Others may not like it, but it's your watch.
Pro Support both round and square displays
Pro Simple
The design of the watchface is simple so it isn't distracting, but it's interesting enough (if you like BatMan at least) to make you stand out.
Pro Batman's chin
Cons
Con No support yet for WebCal
No support yet for WebCal, such as those offered by Facebook events.
A workaround exists. Since this application uses the same background services as Evolution, installing it and adding the WebCal calendars there, also adds them to GNOME Calendar.
Con Poor interoperability with online calendars, does not connect to Fastmail
