I am not sure. The only reason I got my Tracker is because my insurance gave free setup and the monthly charge was worth it. From the many adverts, they seem to offer the same services. But what about their service delivery and success rate? That is the question.
I'm not entirely sure about the differences because I've always been with Tracker. But they have always been professional and their service has been very good. I use their reports as a substitute for a SARS trip-analysis too. At the risk of this sounding like a Tracker promo, they also assisted me pretty quickly when I got 2 flats in a very dodgy suburb - they called a tow-truck company on my behalf and sent an escort for protection while I waited...
I was a Skytrax client before Tracker took them over - not sure if that's the same product now, but also has the logbook feature. The Skytrax product wasn't changed after the takeover too, which was great...