Calligra is on a different path from the mentioned suites. It is first of
all integrated into KDe in ways that LO and OO are not. Secondly it is
structured differently. You get a different experience with LO and OO
trying to follow MS's lead. Once you open Calligra you see the difference.
It is lighter weight, but not lacking in features. The feature set is
different. Upcoming they are trying to be able to make Epubs for example.
Nobody else is doing that.

I love Calligra. I like the others too. I do not have to choose between
them. I have my cake and eat it too.