The world of interoperability standards and protocols has always been one of rivalries and competition, both based upon who is backing who (and thus wants comparatively more power/influence by getting more people to adopt their standards), as well as technical features and superiority. I feel like AP has a much better chance in the long run, simply being older and more established, but also, there's a bunch of sorta messy and vague areas in the protocol that means you can have a completely standards complaint server that still doesn't actually work with other Fediverse servers.
How well the community continues to work to mature the standards and testing layers, but then also which communities manage to continue to attract and grow their userbases will shape the future of which standards grow and which diminish.