I too use the black Kool Stop inserts in my Tektro brakes. Like Garthr, I don't have to ride in the rain.

The original pads squealed and had to be set-up carefully to avoid that. They weren't very powerful.

I then fitted the latest Shimano pads which also required careful set-up to avoid squealing, however, they had a much higher friction coefficient and worked well.

Finally, I fitted Kool Stop black pads. They are quiet, have the highest coefficient of friction and seem to be very easy on the rims. Set-up was easy and I haven't had to readjust them. I've fitted them to both my working bikes and shall use no other pads.

Joe