I don't host yet, I build AI automations for property businesses, so I see this from the other side. For guest messaging, the platform matters less than the plumbing. Let the AI only write the reply, and let a workflow tool like n8n or Make decide when it sends and log it. Then swapping ChatGPT for Claude is a ten-minute job, not a rebuild. If your GPTs hold your property details inside their instructions, move that data out first.