Chevalier d'Eon or Martha

Hv problem deciding btw the two, need advice from veterans of this game. My current 4 * and 5* are:

1) Orion
2) Shuten Douji
3)Sanzang
4) Atalante
5) Marie
6)Stheno
7)Heracles
8) Tammo Cat
9) Beowulf
10) Astolfo
11) Helena Blavatsky
12) Rama
13) Emiya (assassin)
14) Irisviel

Notable 3 stars which i have level are :
Cu Chulainn (already at max lvl)
Medea
Julius Caesar

For recent events I have been using Marie and Cu Chulainn as both helped me survived bosses with ease. Both are already at Max lvl, same as Heracles.