Now let me explain.
KE81 has the Hochfir (a pretty goot smg) the Caulden (a very forgiving pistol) and the Beckhill Combat Knife (one of the more reliable melee weapons). As for augments it has Extra Supplies, Potent Packs, and most importantly, Cool. The combination of both Potent Packs and Extra Supplies has already been talked about as an excellent combination, both perks either directly or effectively reducing the cooldown for his Healing Pulse.
Since the last balance patch, however, Phoenix got a buff to his Self Revive, changing the cooldown to only 25 seconds, which is almost a use for every spawn wave. This is where Cool comes in. due to the nature of the MG turrets, after being downed while on the MG you will be blocked from enemy fire (coming from the front), allowing you to use your Self Revive to keep going. This lets you stay on the MG longer without as much risk and actually take advantage of the Cool augment. I would take that over Untrackable any day.
So hooray to those who have the Phoenix Obsidian