Tech II clone test on 2006 C6:It's great

Here is the review on 2006 c6 with GM TECH II scanner

I just checked my Tech II clone against my 2006 C6. In the ABS section there is an "Automated Bleed" option. In the Radio section there is a "VIN Relearn" option. I've never actually used either one, but I bet they work.
The clones are literally running the same software as the Tech II, so they have all the same functions. There are a few caveats: the standard clone power supply will cause the unit to reset if you run the starter motor, apparently, though this can be fixed. Also, operating while tethered to a PC involves a bunch of licensing hacks and other nonsense. But you only need to do that if you want to flash the ECU firmware.
The Tech II lets you see (and individually reset) all the DTCs from all the modules. It also has a bunch of special functions and bidirectional capabilities.
It's great as a standalone diagnostics tool but it isn't intended to modify ECU parameters like tuning software does. This is a tool for fixing the car, not modifying it.