Before the Circuit Playground Express, there was the Circuit Playground Developer Edition (now: “Classic). They look almost the same, but there are some small, yet important, differences between the two iterations (see the table with the overview). One is very important: the processor is different and the Express has got 2 MB of flash memory.
Because of this difference, the Circuit Playground Express, unlike the Classic can be programmed using this online programmer. It uses a Blockly like language, in an environment very similar to what you can use for the Micro:bit. This of course makes it more suitable for use in schools and with younger students with less experience in programming. With the Classic you had to use the Arduino environment to program it.
Another difference between the two versions is the infrared receiver and transmitter, allowing for data transmission using infrared light, similar to what the Puck.js does. It also can be used as a proximity/distance sensor. You can hear lady Ada explain how that works here.
Resources for the Express are still somewhat limited, the board is still very limited in availability which was one of the reasons why I was very glad that after it actually was in stock for a couple of hours last week, it was sent and transferred from the US to Europe in exactly 7 days. Not bad. It is a bit more expensive than a Micro:bit, which you currently can buy direct in the Netherlands. We’ll see how this develops. If you’ve got any questions related to stuff that I could test with the Circuit Playground Express, let me know.