Clearly with the improvements to Code, elementary OS is aiming to provide a usable desktop that’s also a good platform for development. I suspect most developers will probably want more familiar tools, but elementary OS does make a good development platform.

What is elementary OS good for?

elementary OS is great for casual use. It’s great for writing. You can even do quite a bit of gaming. But many other tasks will require you to install a number of non-curated apps.

Which is better Ubuntu or elementary OS?

Ubuntu offers a more solid, secure system; so if you generally opt for better performance over design, you should go for Ubuntu. Elementary focuses on enhancing visuals and minimizing performance issues; so if you generally opt for better design over better performance, you should go for Elementary OS.