Doing some reading it looks like the X-Rite Display Pro and Munki have the higher quality hardware. But the X-Rite smile has lower quality hardware than the spyder so if you are looking for the low end budget color meter you are best off with the spyder express over the smile. If you want the higher quality color meter though you are best off with the X-Rite munki or the Display pro since the only difference is software.
Also, the argyllcms with dispcalgui if supposed to be better color meter software than what comes with the smile or spyder express. I don't know how it compares to the higher end software that comes with the better meters though.