I believe you can use the Passport software with your existing ColorChecker.
The advantage of the Passport hardware is in its design. It is better for field use because it can be snapped shut to keep debris off the patches. It can also be propped up and oriented at various angles. There are also additional patches as mentioned in Michael's review which can act as additional "white balance presets" -- creative warming/cooling, etc.
On the whole concept of accuracy and evaluation, one of the problems with doing numeric evaluations is inherent limitations of the color matching model. For example, L*a*b* comparisons via Delta E 1976, or any of the newer metrics, are based solely on colorimetry with assumed viewing conditions which often do not match the actual photographed scene conditions (e.g., photographing a ColorChecker in bright daylight versus in a dim room may lead to very similar reported L*a*b* values but very different actual appearance of the chart). You may have noticed that if you try downloading a reference ColorChecker image (Google search should turn up a few) and view it on your display, even with a well-profiled display whose gamut contains all of the patches, the tonal contrast does not look the same as the real thing.
The other problem is that optimizing for chart reproduction does not necessarily lead to better results on real images. Obviously if there is a significant problem with an existing profile (e.g., blues are coming out green) then a custom-built profile from a chart you've shot will fix that. But when one starts getting into nuances of exactly what shade of red you're looking for, it's not so clear. There are cases where optimizing for the chart (e.g., red patch) will give you a perfect hue reproduction of that patch but not so good reproduction of other real-world red colors. This can result from camera metamerism and cannot be addressed by a single color transform (profile).