L3 is the parent of Chelton (like Honeywell with Bendix/King), and the overall name under which the Chelton systems are sold. If you know the Chelton systems, you know the L3 systems.
As for Avidyne, I agree with those who say that as long as it's in Cirrus (and Alan K seems to like it, so that should continue), it will be quite viable.
Finally, I prefer the Avidyne system to the G1000 because it has the actual radios in the panel, not invisible behind the G1000 interface. If you lose the Avidyne PFD, you can press on with little trouble with the three flight instruments, the MFD, and the 430's (I've trained folks to do that, and they pick it up easily). If you lose the G1000 display (and there's a single point failure that can take out both displays), you are deaf, dumb, and blind. Even if you only lose one G1000 display, you have to look/reach a lot farther cross-cockpit to fly off/control the right side screen than you do using at the 3 flight instruments and the 430's with the Avidyne set-up.