So King of Hell is decisively stronger than his normal CoC usage, thanks to an oversupply of CoA in addition to CoC, according to all Zorostans, but when it does not fit your argenda, that SAME oversupply of CoA suddenly does not make a difference anymore (Rooftop Tatsumaki + Hiryu Kaen) and the only thing that matters then is the stamina drawback? Ever heard of double standards, mate?
Enma if released, is obviously a great power amplifier, as we have seen from the first monent Zoro used it, when it cut off a cliff with a massive haki release, while Zoro was barely putting in some effort. Even tho it comes with a certain drawback, it still opens up new possibilties.