Either is fine, the AI generate text card should give you a chatGPT style response to your prompt it's very much like a Reese cup in this scenario there is no right or wrong way per se, but the implementation of chatGPT call will require a openAi key generation as well as actually having the data sent there to be written. The Botpress AI generate text is built in and in my humble opinion just as powerful and maybe more customizeable with more ease. These are simply opinions nothing wrong with going the gpt route just more cards in the flow and probably increase in response time.