When do I actually need the Pro version?

Three main signals that Free is not enough: (1) Your store sells WooCommerce subscriptions – Free treats subscriptions like regular products and does not cancel renewals upon withdrawal. (2) You sell bundles (Product Bundles) – Free cannot correctly calculate the refund for a partial bundle return. (3) You handle more than 5-10 declarations per month and want refunds created with one click instead of manually clicking through all line items. If none of these apply, Free usually suffices.