I have been following Zero9 for a while, and I do agree that they need to step up their game. The only things they're advertising is the fact that their visual is a Korean and a member is Taiwanese. They sing okay, they can't dance, they don't advertise well, they don't interact with the fan base. Nothing. It's a disaster overall.
I wouldn't give up on Monstar yet though. Monstar is still the most popular at the moment, and they're in the middle of a comeback series. Meaning they're releasing multiple MVs through the first few months, and one of those MVs will reveal a new member. I'm hoping the new members will be vocalists to balance out the group. Monstar is supposed to have 5 members, after all, and it's confirmed that they will.
Uni5 is rising in popularity due to their looks and dance, not much so the music, but it's getting there.
But let's be honest here, none of the Vpop groups are popular mainstream. The mainstream ones are always solos. Monstar and Uni5 haven't reached mainstream yet despite having an organized fan base.
Now let me introduce a new group, Usagi. https://www.facebook...Usagigirlgroup/
They're debuting in June. Their fandom name is Teokbokki. Yes, I'm dead serious. Their group name is Japanese and their fandom name is Korean. From what I've seen, they can't dance, and is a visual group. Not sure about their music. But I don't have high hopes really.