Do anyone have experience with this in comparison to vega?

As an aside, wikimedia is switching all their chart support from vega to echarts.

I'm not an expert on either, but my impression is that vega tries to do literally everything using a custom json syntax which can get confusing and unwieldly. Echarts is a bit more straightforward at least for the simple case.

Vega has a questionable security track record which is concerning if you let untrusted users define graphs.

We use Vega pretty heavily, its a broader ecosystem. Where it really shines is in combination with Altair and Vegafusion to do number-crunching on the backend and return a chart spec that can just be rendered on the front-end.

That makes it particularly useful when building interactive visualizations with a lot of data.