When comparing Elementary OS vs KDE Plasma, the Slant community recommends KDE Plasma for most people. In the question“What are the best Debian-based Linux distributions?” KDE Plasma is ranked 42nd while Elementary OS is ranked 51st. The most important reason people chose KDE Plasma is:
Included file manager provides several icon, list and detail views to choose from along with features such as tabs, bookmarks, tagging, previews and metadata, network file access, bluetooth file transfers to/from devices and excellent removable storage integration while remaining fast and easy to use.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro UI design consistency
Excellent uniformity between all the stock application and an overall extremely clean design with simple animations.
Pro Lightweight & fast
Runs well on limited-resources hardware, including netbooks or chromebooks.
Pro Built on Ubuntu
Built on Ubuntu LTS with all its qualities and support.
Pro If you like MacOSX the UI/UX is similar
Pro Extremely user-friendly
This distribution promises you a very tailored user experience and it does deliver on that promise. The developers provide you with a custom desktop environment and a set of neat programs. And the whole desktop looks simply gorgeous.

Pro Active Google+ community
There is a place where Elementary users can ask their questions and usually get answers pretty quickly. Not only by the other users, but the devs are pretty active themselves, often engaging in the discussions on the hows, whys, and plans of the OS.
Pro Simplicity, limited configurability
Sane defaults with less confusion for new users.
Pro Consistent development practices
All Elementary apps are written in Vala and hosted on Launchpad, and there are standard APIs such as contractor for applications to interact with one another. This is different from most distros, in which apps are written in a variety of languages. This design decision makes it easy to get started developing for Elementary and to understand how the various pieces fit together.
Pro A dedicated StackExchange site
Elementary OS has a dedicated StackExchange site where users can easily find answers to common questions.


Pro With new tweak tools customisation is not a problem
Now the OS is amazingly customisable
Pro Has a file manager that provides a good balance between power and simplicity
Included file manager provides several icon, list and detail views to choose from along with features such as tabs, bookmarks, tagging, previews and metadata, network file access, bluetooth file transfers to/from devices and excellent removable storage integration while remaining fast and easy to use.
Pro Highly flexible
There are many customization options and possibilities to tweak the desktop, including widgets.
Pro Looks beautiful
The design of the three built-in desktop themes; Air, Breeze, and Oxygen, are very beautiful to some.
Pro Adheres to standards
Standards adherence allows for interoperability and shared technology for X Window System desktops, with similar Wayland support being worked on. Applications not written with Plasma in mind work very well in Plasma as a result. The development team has also been instrumental in standard creation and adoption such as NETWM, X11 clipboard, icon themes, mimetype handling, application menu standardization, system tray protocols and notifications and more.
Pro Keyboard friendly
Nearly all actions can be driven with keyboard commands. Window management, including effects such as desktop overviews, can be triggered with a keyboard control (or mouse gesture) and some even support filtering results (such as windows shown) by typing. The KRunner tool (default keybinding: Alt+F2 or Alt+Space) provides searching local files, online sources, unit conversions, math and more all from a keyboard driven interface.
Pro Comes with a suite of powerful applications
Plasma Desktop generally comes packaged with a full set of applications to get users started, including a file manager (Dolphin), advanced file manager and browser (Konqueror), image and document viewers (Gwenview, Okular), the Calligra office suite, CD and DVD authoring (K3b) and dozens more. The desktop can be installed and used without these applications, but they add significant value for many people.
Pro Integrated advanced search
Plasma Desktop comes with an integration search system that makes it easy to find local files, emails, contacts, events and more. The file manager supports tagging and rating files as well as full-content searching and the KRunner command window and the Milou desktop widget makes searching for files, emails, applications and other content by name, subject, category, tag, fulltext, etc. very simple. It does this with essentially no noticeable interference with day-to-day usage of the computer, thanks to the scheduling built into the backend system (Baloo).
Pro Multi-device "convergence"
Plasma Desktop provides seamless "zero config" integration of your Android device with your laptop and desktop machines via KDE Connect. Phone calls, SMS messages, cross-device copy and paste, media remote control, cursor control and more are supported.
The technology that Plasma Desktop is built on, simply called "Plasma", also provides interfaces for phones, tablets, netbooks, and media centers in addition to the desktop. These additional interfaces use the same underlying frameworks and therefore work well together and have a unified feel to them. They also support a common set of applications across them which adapt to the input methods and screen sizes.
Pro Great HiDPI support
Scales well with laptop and big home theater screen simultaneously.
Pro Bunch of coherent applications
What make plasma so nice is the galaxy of apps, sharing same look and feel, configuration and behaviour.
Pro KDE is an evolution on the classic desktop model
KDE 4 is a great evolution on the classic Win95/Gnome/XFCE approach. It's moving in innovative directions while respecting the classic metaphors.
Cons
Con UI doesn't let you change anything
Every installation of elementaryOS looks exactly like the same.
Con Old base and applications
The slow release schedule makes the applications outdated. It drags behind Ubuntu LTS (on which it's based) which itself drags behind Ubuntu which is often still quite far behind Arch for example.
Con Outdated or bad default applications
Con Poor Linux community reputation
The devs of elementary OS feel anyone not paying for their Ubuntu respin are not worthy of using it. Which upset a good bit of people. Obviously the core dev team have issues with their community outreach and PR.
Con Quite buggy
Con Very slow development cycle
Elementary does not offer any release date for their stable releases going more with an "it's done when it's done" attitude. Making depending on newer apps a difficulty as well as a poor choice for those that need consistent release schedules for their OS.
Con Not very configurable
Con The desktop doesn't let you to put icons by default
Con Limited and outdated packages
Packages can be very outdated, and many can't be installed from official repos.
Con Doesn't support 32-bit hardwares anymore
One can install pantheon DE from new ubuntu's repo but Elementry OS is not making new ISO's nor is it supporting them. It makes confuzzled to new users.
Con Upper panel requires extra spaces
The upper panel in Elementary OS requires more space. This can be a problem for computers with small monitors.
Con Emacs doesn't work
Emacs crashes due to a partial gnome library update.
Con Heavy animations
It has some animations that don‘t run well on older hardware.
Con Window control button placement may be unintuitive to some
elementary OS has window controls on the left side of the window. It may be less intuitive to users coming from other operating systems that put window controls on the right.
Con No proprietary driver installer
Elementary OS removed the driver installer of Ubuntu.
Con Problems with basic functions
Problems often arise with functions like keyboard layout and touchpad.
Con Boring UI
It can be very boring.
Con Stability problems
Under certain conditions, most of KDE's components can be highly sensitive to race conditions, which leads to KDE applications frequently crashing, and, on rare occasion, kdeinit itself locking up.
Con Perceived clunkyness and slowness
Compared to other options, KDE is still perceived slow. Especially, the desktop takes a few seconds to login.
Mouse pointer can feel sluggish, or laggy, on older systems.
Con HiDPI support is great
One can even synchronize the login screen to scale with the rest of the DE
