Beyond (poorly) translated event story cutscenes where characters are first introduced, the majority of each character's personalities are delivered via their voice lines anyways. Which aren't and probably never will be subtitled on Nutaku. Exception being those lucky enough to be main characters in the main storyline quests which have their own set of extensive cutscenes.
I think they could at least implement subtitles to Homepage, where you can click on the girls to hear extra dialogue. But one can only dream...
The translated personal character quests that give unique earrings would help too, but Nutaku seems to have forgotten that those exist and haven't added more than 6 of them since launch.
IMO, I feel like the major reason to play DMM over Nutaku is having lost patience with Nutaku itself as a browser games platform. Which is a completely legitimate reason. Other than FKG, every other Nutaku browser game has been mishandled in one way or another, even games released after FKG.
Otherwise, it's the lack of patience for new content to reach the Nutaku version (no big deal) and lack of freebies, which wouldn't be such a big deal if it weren't for Nutaku's money-grubbing nature as a whole, and tendencies to offer only players willing/able to spend on daily deals.
It's tough luck no matter how you cut it. On one hand, FKG being Nutaku's most consistently well handled game so far means that playing it and supporting it should send a message to Nutaku and give an example of how games should be localized here.
On the other hand, it's still far from perfect and could be handled much better compared to the original version in its homeland. But that's the case with almost every localized game nowadays, sadly.