[pzuraq]

The underlying implementation is the largest difference. Where MobX relies on pub/sub and observables to propagate dirty state, Glimmer’s autotracking uses a lazy system that incurs minimal cost until render occurs. We’ve found the overall performance of this system to be much better, and the primitive easier to optimize.

[wycats]

And on top of that, the fact that we use a simple reactivity primitive under the hood[1][2] means that we have been able to transition from an API designed for 2012-era two-way bindings to a unidirectional data-flow model with minimal disruption, and with free interoperability between code written with the two APIs (even in the same object).

This also means that we can design new functionality (like Octane's modifiers, and other upcoming reactive APIs) without worrying about how the parts of the system will work together.

[1]: https://github.com/glimmerjs/glimmer-vm/blob/master/guides/0...

[2]: https://github.com/glimmerjs/glimmer-vm/blob/master/guides/0...