Like in topic - what do you think, is it better to be able to control server via GUI or command line? I wonder which solution is better - command line should work everywhere and is very easy to make, but GUI should be faster and easier to use and be able to show more data at the same time.
Absolutely depends on what you want to use the server for.
You already said, if you need fast and realtime access, GUI is probably better, but otherwise, command line gives you possibly an easier way to add more varied options.
Server management should be done through a webinterface, where the UI can be as elaborate as you want, without requiring allocation of valuable resources for yet another streamed desktop environment that is lagging all the time.
That, and CLI (SSH access) should be restricted to emergencies.
JMX is another option - user interfaces for this are already available, and emitting JMX data from your server isn’t that difficult. The JVM already does this for things like memory usage and thread activity.
If you want to interact with your server over the web then a web interface is the way to go, but if you’re on the same network and need some sort of interactivity up and running pretty quick, JMX does the job.
Why are you asking?
Are you implementing your own server controller? Are you shopping around for options for yourself?
This is pretty subjective, so I’m not sure what you’re asking. It’s a bit like asking: which is better, burritos or spaghetti?
(burritos is better)
I like the *nix style approach. Command line interface that you can build a GUI on top of if desired. Depending on the approach, it should work equally well with a local or remote/web GUI.