It's hard to define what "better" means. I think each individual has to determine for themselves what that means. What I consider a "better" machine might be the exact opposite of what others think. For example, I happen to like the audio on my ATPro, but others think the Minelab "flutey" audio is where it's at. I personally don't like that. Some say the ATMax is heavy, but will praise a light machine that in reality is only 1 or 2 ounces lighter. Some machines feel better balanced than others, but that's subjective too. I have a NEL Storm coil on my ATPro most of the time, and it feels fine to me. I think one of the things working in favor of the ATMax is the company behind it. Their support is excellent.
I would suggest watching as many videos as you can and draw your own conclusions, but remember, some people have hidden agendas and will try to make certain models look bad. For example, doing comparisons, but not properly ground balancing, or intentionally running the sensitivity too low so that the machine comes in last. There are a lot of Garrett fans, and just as many "haters" so take that into consideration too.
Whatever machine you end up with, stick with it and learn it well.