[archimedespi]

The reason someone serious about embedded development would want to buy Arduino boards is that they're convenient Atmel-architecture microcontroller boards. The ESP8266 may be "arduino compatible", but a large number of those Arduino libraries running on it had to be rewritten.

If you want convenience and ISA/peripheral-register compatibility with existing low-level Arduino code, you're locked in to atmegas unless you want to do some fun porting work ;)

[Animats]

The next step up was the Arduino Due, which is a low-end ARM system supported by the Arduino toolchain. But it seems to have been retired. (Now I find this out. I built something on a Due because I needed more memory and CPU speed.)

[archimedespi]

It may be retired, but Sparkfun still sells it[1].

If you're looking for other faster microcontrollers with Arduino toolchain support, there's a bunch of stuff out there. See the Wikipedia page on non-atmega Arduino-supported boards: [2].

Additionally, if you're willing to learn how to use the ARM CMSIS HAL and write raw C++, there's the STM32 series of microcontrollers. Those also support Mbed, if you want to learn that instead (it's much easier than using CMSIS with C++, it's basically the equivalent of arduino for many 32-bit ARM microcontrollers).

[1]- https://www.sparkfun.com/products/11589

[2]- https://en.wikipedia.org/wiki/List_of_Arduino_boards_and_com...