[idibidiartists]

D3 can use GPU shaders and is far more flexible. This is ok for canned vis, not for custom data vis. Like Vega vs D3. D3 wins every time.

[ruleabidinguser]

What makes D3 more flexible?

[ZeroCool2u]

Vega is built on D3. It's just operating at a higher level. It's like C++ vs Python. You can do anything in C++ you can do in Python, but it may take a lot more work.

[domoritz]

This may be a bit confusing but Vega only uses some D3 helpers, it does not generate D3 code at any point. See https://vega.github.io/vega/about/vega-and-d3/ for details.

But you high-level point is accurate, D3 is more expressive since you can use all of JavaScript.