[oscilloscope]

It's hard to evaluate when the projects are so new. It was a similar problem with Crossfilter/Datavore/Data.js/Miso Dataset when they all came out.

If I had to pick, I'd go with Vega because I think it has the most potential to develop a community around it. Especially as a bridge between Python/R and D3.js through JSON. Think iPython notebooks, R Shiny, etc.

[HarshaThota]

Perhaps this is not the right place but can you expand on the Crossfilter/Datavore/Data.js/Miso Dataset comment?

[oscilloscope]

They are all libraries for managing datasets with fast or convenient filtering. Useful for linking visualizations together through a common data model.

None have become as popular as d3.js though, so it's still hard to compare them.