Lady Loki can get hit by more than Myztero, but she will not send things back to all. A Joon blind will only go back to one hero, a GM burn will go back to 2 or 3 heroes. Myztero may get hit by less ailments but all of them will go back to all enemies. Also, Lady Loki’s ailments will live out their natural duration depending on at which point she triggered her special. Myztero will send all ailments at full duration.
They are different, with some areas where Lady Loki is better and some where Myztero is better. I think it evens out.