I'm currently working on WebKit support in Boxy SVG (https://boxy-svg.com/ideas/95) and SVG rendering performance seems to be actually better than in Inkscape - especially when transforming many objects simultaneously and when manipulating objects with filters applied.

Igalia has made some massive improvements to the SVG engine in WebKit recently: https://wpewebkit.org/blog/05-new-svg-engine.html