When you want to Play Heart Cross, go for it. sumire System gives you a lot of Time (so much time that I become to Slow for other teams) and you can do your combos in nearly every round. But when you have a "perfect" Myr, I think she will outclass Sumire. Myr is better against binds, has an easier gameplay, you can Play different playstyles (Row, TPA) and you have no probleme with green enemies. But like every Heart Cross: Sumire is Great. PS: Sumire systems main weakness is that her skill are ready in Turn 2.