Sorry for asking this question, but, I really need to know:

Do we need "two" Wikipedia ?
Can we really collaborate all toqether and make a good one,

or we need to divide our effort and make two or more office suites as possible ?
Why should I support Calligra instead of Libreoffice ?

Please, I want replies as much constructive as possible.

To have constructive answers it is good to have a more constructive question. Because, let's face it, there are even more than 2 office suites out there.
But you should probably think about how open source works. Someone starts a project just because s/he likes to do it in their spare time, either because of curiousity how to do it or because existing solution don't fullfill a certain need. The project grows bigger and suddenly even more users are using it.
Considering you asked this question means you are aware of calligra, which means there is some buzz about this project, which in turn means some people indeed like to use it.
And that is the magic of open source. You can decide on what project you hack, and the user can decide which software s/he uses, in this case which office suite.
You could ask the same about "why more than one operating system". It is all about diversity and choice, and whatever fits your needs best.

Actually I continusly asking why there is gnome and kde. Both aims are similar, and yet one aside of the other, cant catch the market and finally, end user loose.

I really believe that you and much more people invest enormous to make another suite, but I will support if there was for different plattform, market, etc.

Both targets are exactly the same? Or one should be the replacement od the other? (like xmpp for sip ?)

Again, my question is to be as much constructive as possible, and of course, help me with comparisons.

It's one of the anthropic principle consequences. There can be electrons and protons, blue and yellow flowers, hammer and screwdriver, KDE and GNOME, Mac and PC, Calligra, OpenOffice.org and Libreoffice.

If you disagree with this, you can always choose another Universe to live in.

There is strength in diversity: Mutual inspiration, healthy competition, choice. And there is safety in numbers: Many years ago the Gnome project started because some developers worried that KDE might have become too dependent on a company - what would happen if that company suddenly changed its policy towards open source, or was bought by another company (the latter actually happened, bu to no ill effect). These days you see a similar thing with OpenOffice/LibreOffice. And it could have happened. Placing all efforts in a single project makes us more vulnerable.

Having several projects with similar aims allow the larger open source community to benefit from more experimentation. Some innovations will ultimately fail, and we can all learn not just from our own mistakes and successes, but also from those of the other projects.

Finally, Neverindingos points above are very relevant: It is a mistake to assume that all KDE developers would move to Gnome if KDE were suddenly to disappear (or vice versa). While there are certainly areas where we could benefit from more collaboration, the two (well actually more that two) projects have partially separate goals, and they complement each other as much as they duplicate efforts.

It is sometimes asserted, that we could win over the masses for open source if we could only unite behind a single desktop, a single office suite, or a single distro. I think this is quite naive. Even if all in the open source community did agree to work on the same product it would still be the case, that most machines sold would come with a proprietary system pre-installed, and most users would stay with that. It is not lack of unity that is holding us back, it is the market forces.

I would like to give two answers to this question.

1. Different ways to implement the same thing leads to different strengths and weaknesses. They may also have different long-term goals. Right now LibreOffice and Apache OpenOffice are bigger programs with more features than Calligra. But they are also much less flexible in their architecture and use much more resources like memory and CPU. This makes Calligra much easier to port to new environments like smaller screens and less memory like smartphones. The more flexible architecture also makes it possible to give it new user interfaces like touch based UI's for smartphones and tablets. LO and AOO are virtually impossible in places like that. They are stuck at the desktop where they are doing quiet well.

2. You must not look at where an application is today but also where it is going and where the project's priorities lie. The Calligra team has always emphasized a good architecture with plugins and clear separations between different layers. (If you are not a developer and don't understand this point, just think of it as flexibility.) This means that even if we have less features today we have a very good platform for future development. You can look at my blog post at http://ingwa2.blogspot.se/2011/05/calli ... tware.html where I develop this point more.

I think that in 3- 5 years or so the monolithic architecture of LO and AOO will make them reach dead ends development wise which means that they will not be possible to develop any further without big, big rewrites. This is what happened to Netscape before it became Mozilla Firefox and they had 2 years(!) without a release. Calligra, on the other hand, will always adapt fast to new markets and new types of hardware and will be the project that takes over when the others reach the dead end points.

But that shouldn't matter very much to the user because we all use the same file format, ODF, which makes your data safe.

Sometimes I ask myself the same question. I hate to see open source developers reinventing a wheel and implementing the same features in different programs all over again. I, as a user, would like one great application than n average-to-good ones. But then, I think about it and I see that this is good that we have n apps instead of one.

1. Logic behind statement that it's better to put all developers in one application is:
a) more programmers → more features, faster bug fixing → better software
b) we put more programmers in one app → we get better software (due to a) above).
But this logic is faulty. First of all, fixing bugs and introducing new features depends on programmer familiarity with codebase, his skills and task difficulty. Introducing new, highly appreciated features (such as good bibliographic database feature, table styles or new UI) requires perfect skill and familiarity of codebase. Calligra devs do not know LO codebase, so we will at best have to wait few month (maybe years) before we see them making huge improvements.
Second, programmers have different skills. A thousand programmers with basic C++ will do worse job than few experienced programmers with perfect C++. So if we put all Calligra programmers into LibreOffice, it doesn't necessarily mean that LO get better (disclaimer: I do not mean to say that Calligra devs has poor programming skills. I don't know any of them and I have too poor skill myself to make such bold statements. I am only trying to say that above implication is not tautological).

2. Since we are free people (thankfully most of us are), no one can force anyone to do anything. If we close Calligra and say all their devs "work on LO know", it doesn't mean they will listen. They may prefer to do something else. So again, implication:
less office suites → more people working on one project
is not tautological. We may shut down all office suites out there and won't see any new contributors in LO.

3. Haven't you guys had any biology lessons? We are homo sapiens sapiens, perhaps the most intelligent specie that has ever existed on this planet, because of evolution. And evolution does not unite different species - it divides them. It creates huge number of different organisms with different properties and sees, which are best fitted - which one will survive. If we want the best office suite out there, we need as many of them as possible. The best will survive.
(Sorry about anthropomorphizing evolution - of course it can not "do" or "see" anything. It's just I'm not fluent enough in English to say it any other way.)

4. Last but not least (this one isn't logical, too) - haven't anyone of you heard about dangers of monopoly? Look at Microsoft, IBM, Oracle, France Telecom and many, many others. It doesn't matter if this is open source or not - monopoly is monopoly. And we should do anything we can to avoid it. Competition is what makes software better.

Of course I would like to use office suite with great bibliography feature, table styles and many other things I lack, be it LO, AOO or Calligra. But closing Calligra and moving all it's developers into LO is not a way to achieve that.
(I have taken Calligra and LO as examples, but the same applies to KDE SC/GNOME/Xfce/LXDE/etc., various Linux distributions, Presto (Opera)/KHTML/Webkit/Gecko (Firefox) and many other fields.)