Well the flame pit drains life and circuit and gives your OTG strings a lot more significance. Also if you ignite it, it has several uses. If it catches them on fire, you can get a combo. It can bring them closer to you if they block it on the ground and if they block it in the air, you can throw out a 5C (air unblockable) and have another combo opportunity.
Basically, it's awesome pressure. Also Akiha Vermillion's 22C lasts for 30 seconds versus Akiha Tohno's 10 seconds. After a few seconds, the flame pit will start draining life, healing Akiha Vermillion.