The AirPods Pro and AirPods 3 differ primarily in their earbud design.
The AirPods Pro features an in-ear design, with silicone ear tips that fit inside the ear canal, offering better sound isolation and a snug fit. In contrast, the AirPods 3 adopts a non-in-ear style, lacking these silicone tips, and rests more loosely in the outer ear. This results in a different fit and less sound isolation compared to the AirPods Pro.
Additionally, the AirPods Pro's shape is more compact and contoured to accommodate the in-ear design, while the AirPods 3 maintains a streamlined appearance.