Sorry, I have no experience with Smith's Diamond Precision Kit. But I have a my concerns. According to Smith web site this system has two preset angles 20 and 25 degrees (vs. Sharpmakers 15 and 20) also fine stone has 750 grit.
It is a good tool, depending on what are you using it for. If your blades made from 440, 420 steels and you do not care for high polish edge, it is great. If you blades made from VG10, S30V, 154CM, or other high grade steels, than you will benefit from 15 degrees. Steel is stronger, would have no problem to hold the edge and 15 degrees cuts much better than 20, it is just thinner. Sharpmaker fine stone grit about 1200 and UF 2000, so it would be much easier to create high polished edge, which can be important if for most of your tasks you push-cut.
I love sharpmaker, use it for more than four years. I have standard rod, UF and have coarse and extra coarse stone with grit 80 to use with Sharpmaker. I wish it had more acute angles, but I think I figure it out
This is my sharpmaker with extra coarse stones at 12 degrees
Please, do not forget, 10X eye loupe would help with any sharpening system