What are the best for D3-based visualization/charting libraries when it comes to being high customizable, styleable, and performant? There are dozens of them, but with some research the most interesting ones seem to be:

* Vega - Talked about in this thread

* nvd3 - Meant to work in similar style as D3, supports extension. Seems popular

* Epoch - Real-time charts are purpose-built to be performant and low-overhead. Limited number of visualization types

* D4 - Extends D3 instead of wrapping it. Separation of data from view

* C3js - Easier API. extendable.

* rickshaw - Mainly for time series data. Supports extensions. Works in similar style as D3.