I have a Taylor k-2005 test kit currently (from the PB). I have read many posts that it would be better to upgrade to the k-2006 or the TF-100. I have looked at the Taylor web site. What is the major differences between these kits? Secondly, it appears that there is a slide type comparator? Is this a better way of picking the correct color match? I do struggle at times (my wife thinks that along with all my other deficiencies, I'm color blind too ). Thanks.