I think the biggest difference between Dart and any other JavaScript Framework abstraction is the amount of resources and investment behind Dart. Google has it'

I think the biggest difference between Dart and any other JavaScript Framework abstraction is the amount of resources and investment behind Dart. Google has it's best Language minds behind Dart's VM implementation, its JS transpilation, language semantics and APIs. This is reflected in the rich tooling that already exists around it, include the smart IDE (Dart Editor) which can even infer intelli-sense from string literals inside queries e.g. el.queryAll("INPUT"), rich debugging from both the IDE and inside Dartium (when running native Dart) or inside Chrome with source maps and a rich and consistent library that smooths over DOM quirks. But the best thing I like about Dart is the language, it's a C#/small-talk inspired language with C/JS-like syntax and Erlang-style Actors/concurrency-model. The combination of optional typing, type inferencing, implicit interfaces and convention-based visibility has been the biggest productivity boost for me. It lets me finally have a succinct dynamic language with enough structure that the IDE can provide warnings and intelli-sense while I type. Implicit interfaces means I no longer have to create future-proofing Interfaces and its '_' prefixing for library-only visibility makes it effortless to write APIs.