I want to first say that almost all of the super lines(braid) are about equal as far as quality goes and the different arguments about which is better is in my opinion a Ford VS Chevy deal, each individual has to make up there own mind which brand suits them. I believe Honeywell Corp. holds the patent on the spectra fibers that most of the popular braids are made from, and the differences are basically how it is braided together to make the finished line.
I am not a fan of Power Pro as I feel it is to flat which allows it to cut into the spooled line on the reel arbor, I have no experience with the Slick 8 Power Pro and so I do not know if I would like it better or not.
As far as color fading I have enclosed a picture of some Hi Vis Yellow Tuf-Line XP which is starting its 5th year this year. I take a small section off each spring and check it for strength by lifting wts until it breaks. This year it broke at 26 lbs and was rated at 30 when new. That is 8 lbs more than the maximum drag that is capable from either my Tekota 300's or my 153D Coldwater reels, so it is heading for another season on the lake. Next year I will turn it end for end and use for another (?)number of years.