We had the exact opposite problem! We built a custom webgl rendering layer on top of leaflet to get around leaflet's performance issues. We have now switcher to openlayers and very happy. Guess it depends on the exact use case.
We switched the opposite direction (D3 to Leaflet) on a different app and got a performance speed up for big sets of vector shapes. Seems like there are tons of ways to engineer these web graphics apps and no clear "best solution".
We were just trying to get a ton of circles (electric vehicle ranges) on a map.
We were going to do something to optimize it in OpenLayers by simplifying the shapes, but when we tried it in Leaflet it just worked a lot faster (fast redraws). We think it's something around how Leaflet dynamically switches to a canvas renderer for big datasets.