Eagles, hawks, and the like stoop fast from great height and hit their prey hard. They have strong, stiff feathers and streamlined form for speed in the 'tuck'. This makes their wing flaps much louder, though.
Since owls hunt in much less light and seek smaller prey, they are optimized for stealth, with serrated wing feathers and 'fluff' on the trailing edge to suppress turbulence. That makes them slower fliers and probably reduces their endurance as well.
https://blog.education.nationalgeographic.org/2015/07/24/creature-feature-quiet-as-an-owl/
Did you know most owls can't move their eyes ? They aren't round, but tapered, with the back (retina) end much larger than the front, so free movement is impossible. They've adapted by evolving 270-degree swiveling heads.
https://www.researchgate.net/profile/Andrew-Iwaniuk/publication/227856635/figure/fig3/AS:288945733685266@1445901439968/Dorsal-and-side-views-of-excised-eyeballs-from-four-species-of-owl-a-Northern-saw-whet.png {trigger warning: dissected eyeballs. kind of gross}
Other weird stuff: their ears are at different heights on their heads, giving them audio stereolocation both vertically and horizontally. 
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