I was testing both, individually, and didn’t originally plan on using both. In fact, I was using Boomerang Calendar for scheduling before MixMax became my primary tool.
While I really like X.ai, it is squarely a beta product and not ready for primetime. It often got confused by recipient responses, meeting locations, and types, or complicated scheduling with assistants. I’m sure it will continue to evolve into a robust scheduling AI, but it’s not there yet.
This is primarily why I use MixMax instead. Unfortunately MixMax doesn’t have mobile integration yet, and I’m often responding to emails in transit. For those simpler meetings (usually 30 minute phone calls), X.ai has been the perfect mobile solution that I can CC on an original email or reply and let Andrew take care of the rest.