I don't know much about the Cobra's... didn't they used to make CB radios?
If the dealer is telling you that about Power Commanders they are either blowing smoke up your bum or trying to sell you a product which they have a higher profit margin on. Either way, if anyone started saying things like
they had sent it back 22 times, I'd think they were only looking to name-bash or sell you something else.
PCIII is a very good product, and I've known others who really like the Dynatek line as well. I'm not a big fan of the SERT's since you become tied to the dealer for mapping, whereas the PCIII maps (which there are many custom maps) can be downloaded and loaded up by anyone with a laptop.