difference between Plot and echarts

I am just learning the brand new observable Plot and I like very much the level of abstraction/granularity. Recently, someone mentioned Apache echarts (Apache ECharts, GitHub - apache/echarts: Apache ECharts is a powerful, interactive charting and data visualization library for browser) and at first glance, it seems to aim at the same level of abstraction as observable plot.
I was not able to answer the difference or USP for Plot…

My take on it so far:

  • observable plot has just been released some weeks ago whereas echarts has been build over the last years, is well documented and actively maintained
  • the level of abstraction seems very similar (granularity of API + possibility to customize)
  • API/ conventions will be much closer tied to conventions established by d3.js