There seems to be a huge difference in stability between Icon (Star) and Pinnacle (far better than Champion and therefore a poor comparison to that plastic, but that is the best we have), especially after they are worn a little bit.
In regards to the Cannons, the Icons turn incredibly easily; not necessarily flips, but definitely turns. The Pinnacles will turn a little but most likely only will go right (rhbh) if you have OAT or give it anhyzer. The Canons do not fade much and have a strong tendency to land flat. I like to compare them to longer Z Nukes.
I have to say in general that I am very impressed with Legacy discs. My Pinnacle Canon is my big boy disc, allowing me to throw anywhere from 380-440, depending if I have enough sky to work with. I recently acquired a few Pinnacle Rivals and Patriots. There is a little overlap between those two discs, but no more so than what I have with my TeeBirds and Leopards.
I am not a big fan of the Icon, at least in the drivers because they seem to be a little more susceptible to turn, but my exception is that I absolutely love my Icon Ghost. It flies incredibly close to a Star Rancho Roc, maybe a little straighter and definitely a little longer. I can only imagine that if the difference between Icon and Pinnacle holds true that the Pinnacle Ghost hopefully coming out soon will be closer to a Hornet.
I already have made the Canon and Ghost staples in my bag, and maybe after a little more working them in I would have no problems adding the Rival and Patriot. Right now I would see no problems with making the Ghost-Rival-Patriot-Canon the back bone of my tournament bag. Now, if I can just figure out putters. I am using Ion and Anodes, but I have two Icon Clutches and I am trying to like them.