Compositing math in SVG

Hello,

I am working on graphics application where we need to implement
compositing operations also called blending modes such as soft-light,
hard-light, etc.

The math you use here:
http://www.w3.org/TR/SVGCompositing/
is different than the one in the official Adobe reference
used for Photoshop and After Effects.

Could you please give me some feedback on that, why is it so, and which
one should I prefer?

Thanks