I know this post is old but I don't think this is warranted it's own post. I have Andra 30 Rims with Paul Touring Canti's front and rear and have been riding this config for two years now.
I have spent quite a bit of time with both the Swissstop Blue and the Koolstop Black CSS v-brake pads and have come to much prefer the Koolstop. I have done several back and forths between those pads and have found the koolstop to be grippier, quieter (almost no squeal at all), and overall better pad. I do think it wears a little faster though.
As usual though in the rain they do take longer to stop, I don't think there is much of a difference between the Swissstop and the Koolstop there.
If you are in North America and want the koolstop pads, you can email koolstop directly and they will hook you up.