It’s best to check both options before proceeding, as some businesses do offer a cheaper subscription service when working directly - however as mentioned that may come with strings attached.

I feel the success of small developers relies on IAP, it means I can purchase from them without needing to trust them - the app stores do a good job of reviewing the app for malware and if the app doesn’t live up to expectations it is trivial to get a refund from the various app stores.