both are great, both have weaknesses, depending on your needs.
black strips down to 3-4 strands (can't remember which), but is still black....if you're very pale, it's noticable, (WAY LESS than the thick Mesika thread....and if you know the Mesika thread, it's pretty invisible as is)...the clear is completely invisible....but it has more of a glare than the black, so lighting is VERY important with the clear.
I'm sure if you order one from PrecisionMagic's website, and say that Phil recommended you order it, the very generous David Mann (owner) will gladly send you a spool of each black and clear to try. He held that type of promotion for a while, not sure if he's still doing it.