In terms of GDPR/privacy, is there any issue when posting private data to a 3rd-party server (i.e. webhooks) vs having that 3rd-party query your server? Or can

In terms of GDPR/privacy, is there any issue when posting private data to a 3rd-party server (i.e. webhooks) vs having that 3rd-party query your server? Or can you just say that once a secure webhook subscription is established you are off the hook (pun not intentional)?