I’m about to have to make the same decision. Already have Panther, Khiona, and Sartana maxed. Only 5* healer is Mother North. All of this points to Kunchen being the choice, but MAN it’s hard to pass up the chance to max Hel!
(I’m still four tabards away from being able to max both, after today’s Springvale offer.)
Both fem.Satan and Cage Burrito are strong and fast/very fast. With Hell’s power on their side you could likely kill off your opponent before needing to heal.