Noise Cancelation
The marquee feature for AirPods Pro is Active Noise Cancelation, which uses a mix of hardware and software to block out external noises. (There’s also a Transparency mode for those who don’t want ANC.)
While Powerbeats Pro feature noise isolation due to their in-ear fit, they actually don’t have any type of active noise cancelation feature. That is, arguably, the biggest difference besides design and form factor.