When comparing Kendo UI vs Vaadin, the Slant community recommends Kendo UI for most people. In the question“What are the best Javascript UI Widget Toolkits?” Kendo UI is ranked 1st while Vaadin is ranked 12th. The most important reason people chose Kendo UI is:
Kendo UI is separated into a commercial and open source frameworks. The core of Kendo UI is in the open source frameworks, but some usability and benefits of Kendo UI are lost without the commercial version.
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Pros
Pro Free Core tools
Kendo UI is separated into a commercial and open source frameworks. The core of Kendo UI is in the open source frameworks, but some usability and benefits of Kendo UI are lost without the commercial version.
Pro Platform-based UI
Kendo knows what device it is being viewed on so it can adjust the UI accordingly. If a user is on a PC the user will see things differently than on a mobile device. Between iOS and Android the user will also notice a different as it pulls from the core UI of those core systems.
Pro Theme Builder
An interactive tool that has been created to customize an apps theme. Users are able to select from many pre-defined themes, edit them, and download the theme to bring into a project.
Pro Compiles Java to JavaScript
Vaadin uses GWT to compile Java code into JavaScript. This means that developers using Vaadin can write both frontend and backend code in Java.
Pro Easy to use
Vaadin has a 'design mode' which allows developers to drag and drop components into a canvas and then provide the logic for every component. There are also a lot of third party tutorials and guides which help with the initial learning curve.
Pro Top notch documentation
The book of Vaadin is a must have for every developer that uses Vaadin to make web apps. It is an excellent reference manual and all around a great tool for every Vaadin related need. You can find and download the pdf online or get it for free in almost any Vaadin sponsored conference.
The online documentation is also very good. It has some tutorials and video guides.
There is also a vibrant community which sorround Vaadin, for any problem you may have there is a big chance that someone has already asked and answered that question on StackOverflow or in the Vaadin forums. If not, it will probably be answered quickly if you ask it.
Pro Modern, configurable theming
Vaadin comes with the Valo Theme, a Sass-based theme and engine that calculates styles based on configurable variables and making it easy to define a completely new theme with a few lines of SCSS.
Pro Easy to develop prototypes quickly
Vaadin has what is called the Vaadin Directory which is a repository of downloadable Vaadin components which can be easily used for development. To use something from the repository, you need to download the JAR file and add it to the project.
Cons
Con Expensive commercial tools [$699, $1,499]
The other core tools developed with Kendo are the commercial tools. There is the Professional version for $699 that will result in more jQuery UI widgets and client support. The $1499 "DevCraft" Complete edition gets developers the DevCraft .NET toolbox, testing and debugging frameworks and applications, as well as priority support.
Con Weak scalability
Since Vaadin stores the UI state and logic in the server, this means that for every user interaction a request needs to be sent to the server and the client needs to wait so it can know how to react. This leads to higher traffic and load times.