There should be multiple threads on the tracker as I started many. I have thrown both and currently carry x trackers, so I'll give you my take.
First, the starfire is faster and more overstable. It fades left for me, or rather finishes left (that's fade isn't it?). When new, I could not turn it over. It beat up quick for me this summer, but I believe it was due to how much I was throwing it more than an issue with the plastic. I was starting to turn it over when I lost it. In fact that is how I lost it, I tried to throw a straight shot at a basket with a pond to the right, and it turned. It reminds me of avengers, which is what replaced the starfire in my bag.
Second, the starfire was much longer for me than the tracker. The starfire will yeild long straight distance (especially as it breaks in), but I was still getting it to finish left where the tracker finishes straight.
In summary, the starfire is a fast, overstable extra long driver. The tracker is a slower (than the starfire) stable long driver. BTW, I don't usually look at ratings; this is based solely on throwing the disc. Also, I don't have a cannon for an arm. I would imagine big arms would say the starfire is stable, not overstable.