Hi there,
Thanks for considering our plugins!
The key difference is that WooCommerce Tickets allows you to set up and sell tickets using The Events Calendar and WooCommerce (both of which are free).
Events Calendar PRO has different goals unrelated to selling tickets – it extends the capabilities of The Events Calendar with new ways to view the calendar (like week, photo and map view) and with additional systems such as recurring event management.
If your primary goal here is selling tickets to classes, I’d imagine you only need WooCommerce Tickets.
Does that clarify things?