Can someone explain the difference between these two Arduino variants?

[davepl]

I have long used:
platform = https://github.com/platformio/platform-espressif32.git

However, I recently found that there is:
https://github.com/espressif/arduino-esp32

What I'd like is a stepping stone off of the classic Arduino SDK and I thought perhaps this was it - a way to build for esp-idf without abandoning all Arduino libraries. Is that the case?

Thanks for humoring the naive questions!
Dave