So there's the Love Eve route, the Love Cassie route, and the Love Both route. After playing all three, I've got to say the Love Both route is truly amazing. The emotion that's put into the writing is fantastic.
I also played Cassie's dom route and Eve's softcore sub route. (I didn't know there was a hardcore sub route until I came to the thread.)
Cassie's dom route lacked passion, and has already been commented, this makes sense because of the fact that she's just parroting what she's observed without any real understanding of the delicate balance between dominance and trust that needs to be there.
Eve's softcore sub route nails that balance perfectly, in my opinion. MC loves Eve and, while he wants to dominate her, he also wants to protect her. And because Eve feels that love and protectiveness, she's able to submit knowing that she'll be safe.
The Naughty Captain, in the future will the MC be able to date Cassie (love route) and, together, softcore sub route Eve? If not I'll focus on the Love Both route, but I think having all three together as a dom-couple caring for their mutual sub-lover would be amazingly hot.