As for why does author of BAMT push new users towards cgminer. He feels phoenix is superior. Some of us disagree but he has marginalized cgminer in favor of phoenix. That likely isn't ever going to change.
Purely speculative, but I think using phoenix allows an instance of the miner for each GPU. Thus you can can monitor each process independently. You can then kill and reload that specific hung process through the OS whereas cgminer doesn't quite offer the high level monitoring/control. If a card hangs in cgminer, you're at the mercy of cgminer to recognize the fault and try to re-initialize that card. From my experience with cgminer, if this occurs it generally means a full system hang, but I've not played with phoenix to see if a hung process operates in a similar manner.
Again, purely speculative based off my experience, I could be way off.