Isomorphic software provides SmartClient, the most advanced, complete HTML5 technology for building high-productivity web applications for all platforms and devices. SmartClient's powerful device-aware UI components, intelligent data management, and deep server integration help you build better web applications, faster.
(from their website at https://www.smartclient.com)
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Pro Good documentation
There is an online showcase and a 100+ Getting Started guide
Pro Advanced UI widgets
Layouts, grids, forms with a lot of builtin functionality.
Con Expense: Free LGPL version but expensive to leverage the real power of the framework
The Developer version starts at $745 / Developer
Con Difficult to integrate with other frameworks like React, Vue, Angular...
SmartClient has it's own layout mechanism and doesn't have anything like Kendo UI's framework support for Angular, React, Vue, ..