Flower of Evil is darker in tone, but the two have core similarities. Both shows have a blend of romance and mystery/action going on where, even without the romance, the plot keeps you engaged and you want to keep watching to unravel the mystery. Both also have a heavy theme of hidden/repressed identities (and memories), and both ML's identities specifically have been kept from the FL, to some extent for their safety. Seeing the switch/blend of the two identities the MLs possess is really fun (in Healer) and interesting/thrilling (FoE). I also like that both FLs are very strong and determined in their own ways, often even helping the MLs rather than just being damsels in distress (such is especially the case in FoE).