At first I thought, hands down, clean disbandment - but then I really got to thinking after someone mentioned SM and how they rarely disband, so they can keep profiting from the brand the groups have made, and realized that with some terms met I think a hiatus (in some cases) isnt too bad. The cases are limited, though, and the terms would have to fit specifics too.
If the group technically was doing sub unit work, solo work, or was open to do more of said solo work on their own (like modeling, acting, performing in different areas of the arts, doing fashion work or writing music, doing radio DJ or MC hosting, etc) while still having the solid backing of the group and the other members (given that they all get along and there isn't some sort of tension between them etc) and were receiving royalties from their work with the group name attached, then even though it would be hard for a comeback to have a larger impact due to gans leaving, I would be okay with it.
If the above was not met however and they were missing out on opportunities like the aforementioned because the company wouldn't let them while "part of the group" and essentially dungeoned them, then no. Definitely clean disbandment.
I would go for whatever is best for the idols honestly, in their given situation and with their given company.
As a fan, it sometimes sucks when a group is more on a hiatus, but when the members of said group can achieve and participate in things solo while being on a group hiatus it isnt that bad and I know they are getting to do what they want simultaneously, even of I'm not going to be getting a group comeback soon or at all.