I'm just having a look at css vs js animation and discovered that inkscape isn't loading and saving my script that's in the svg file.
the main difference between css and js is css has limited ability for interactive animation and doesn't support dynamic animation. apart from that CSS seems pretty feature rich.
I'm just writing a dynamic/interactive rubber band animation effect in javascript to check the limitations of css comparatively. I don't think CSS would be able to support things like shape morphing either unless it's all precompiled.