The difference? I have an ad-blocker in Firefox, but not in Google's app.
So Ad-blocking > AMP > Regular (as far as user-experience from a speed perspective). Obviously Google has a lot of incentive to make sure people don't go the ad-blocking route.
Though not sure what is keeping ad-blocking from growing given its superiority - likely just a lack of awareness about the option. If ad-blocking ever did grow massively though, the internet would change in ways we haven't yet seen. Either ad-serving companies would win the arms battle and ad-blockers would become ineffective, or, the web would have to move to a new payment model (Brave-like perhaps).
I'm not entirely sure what the ideal is - likely a model where users can choose between ads or micropayments is the most pragmatic world.